Note: this, like all rankings, is entirely subjective and based on the experience of the writer. Different players will rank creatures differently and all rankings are valid.
When playing a new video game one of the most important things to study before getting too far into the plot is the type of enemies, monsters, and creatures that lie ahead. One needs to know what creatures lie in weight, where each creature is most likely to appear, how strong each creature is, and how to defeat them. In Fallout 4, there is a myriad of monsters that fill the wasteland and are waiting for players like you to venture into their midst. But do not let this intimidate you or prevent you from playing the game because a little bit of research goes a long way. Allow this ranking to act as a guide through the wasteland. Follow it, learn it, and study it. Learn which creatures can be extinguished like birthday candles and which should be avoided at all cost.
It is important to note that creatures that are considered "enemies" in Fallout 4 are creatures that are programmed to be rather unfriendly to the player by default. Without ever even having interacted with the player, these NPCs will dislike them and act in accordance with their default relationship standing. However, cats are one of the few creatures that present no inherent risk. Cats can be used for meat and some players enjoy making trophies out of them after they have been slain.
I think that we can all agree that radiation and wild animals are not the best combination. I mean, some of the animals, like the Radstag, end up looking exceptionally rad (as the name implies) but I would not want to stumble across any of these animals out in the wild. Luckily for players, these creatures are actually quite docile and usually do everything that they can to avoid conflict. If they cannot successfully avoid such things, they are very easily dispatched which places them on the weaker end of this list.
In Fallout 4, Triggermen are enemies that exist as a sort of 20th-century mafia. Because of this, they operate by a strict honor code that must be upheld at all costs. They live outside of society for the most part however certain parts of the story include the Triggermen so they can not be entirely avoided. It is important to note that not all Triggermen will be unkind to the player. Some will be less than friendly, others will be neutral, and some may even be friendly towards the player as the story requires direct interaction between you both.
We all knew that roaches were going to survive the end of the world as we know it and the Radroach is the weird little version of the traditional cockroach that came to be after the nuclear fallout occurred. Though they are quite territorial, they are very easily dispatched and are little more than a slight annoyance. It is important to note that certain NPCs (like Vault 101 security personnel for example) can be taken out easily by these creatures even though they are little more than an obstacle to the sole survivor.
16 Stunted Yao Guai
The Yao Guai are essentially large and intense mutated bears that are not the biggest fans of the sole survivor. Though they are known to be affectionate and kind towards other members of their own species, they are not too fond of the player character and make this distaste well known. However, the Stunted Yao Guai present a much-lessened obstacle that their non-stunted brethren. The Stunted Yao Guai are afflicted by several malformations that limit their abilities and make them much easier to dispatch.
These icky little creatures are the worst creepy crawly around and should be avoided at all costs. Not because of the threat that they present but rather because they are uber gross and something that should simply be avoided. These little creatures can burrow through the ground at super speed and pop up like angry daisies, ready to strike any intruder that crosses their path. They can also rest inside other deceased creatures to a surprise appearance and that it just rather unpleasant if we are being honest.
These mutated scorpion-fly combinations are highly defensive and not a fan of anyone that comes anywhere near their hive/home; even if said person is just attempting a friendly visit. They exist in many forms and love to pursue the sole survivor in large swarms. Though they are not the most unfriendly creature on this list, they are not a bunch to be trifled with and are best left alone. Do your best to avoid them.
As someone who is not a fan of regular scorpions, the idea of a scorpion that has been mutated by excess exposure to radiation which has made them more venomous and unfriendly than the typical scorpion sounds like an absolute nightmare. I would rather experience that recurring nightmare I have where all my teeth fall out continually until I wake up than ever having to interact with a radioactive scorpion. Be careful when dispatching them as same subspecies can release radiation after their lives have ended.
12 Mad Brahmin
It's a cow. It's a mutated cow from the post-apocalyptic future. The best thing about these creatures is that when one is born without any obvious mutations, the "normal" one is considered mutated. That is amazing. The standard variety has several uses as they can be used as meat or assistance for certain tasks and are normally considered rather docile. However, the Mad Brahmin are not friends and are known to go after players whenever they spot them.
11 Wild Mongrel
As the name implies, these creatures are a form of dog that is definitely not man's best friend. Nope, not at all. Not in the slightest. The most unfortunate thing about these creatures is that they tend to come in packs which means that one of the mongrel's present could be far more of a threat than his friends. Oh, joy. Fun fact: the developers gifted these creatures with some of the same idle animations as they gave the players canine companion so some players have reported seeing them play with teddy bears briefly.
10 Feral Ghoul
Feral Ghouls have lost their humanity and, because of that, are driven entirely by their animalistic instincts. Which is not a good thing for those who cross their paths. Though they are easily dispatched if one's aim is true, they tend to pursue in packs and their zombie-like nature can make them rather overwhelming when they appear in greater numbers. They are not the most fearsome creatures on the list but they still present a bit of an obstacle.
As someone who is not a fan of bugs (they are honestly one of my biggest fears next to clowns and angler fish,) the idea of a giant mutated fly that targets people is just the worst thing I could possibly imagine. They use their larva like projectiles to incapacitate the player and will not stop until they are stopped. And that is just unacceptable. They like to pursue in swarms and are proficient at both long range and close range acts, which makes them rather annoying creatures.
8 Mirelurk Queen
The Mirelurk is, essentially, a species of mutated sea creatures that exist within the Fallout 4 world. Their shells protect them (to a certain extent) from the sole survivor's attempts to dispose of them. Though the normal versions of the creatures are comparably weak, the Queen is rather powerful and difficult to beat. She can withstand so much damage and can also deal out a lot as well. Be careful when attempting to dispose of her for she will not back down without a fight.
Synths are a type of android that was created to emulate human appearance and behavior to a nearly imperceptible degree of accuracy. They were created with the idea of creating the most perfect human being possible but the perfection had a price. They are armored, relatively trained, and are not the biggest fan of authentic human beings. They exist in many different forms, each form having its own techniques and weaknesses. However, it is important to note that since they are synthetic life forms it is difficult to dispatch them as they can continue pursuing the player even when their limbs have been removed Monty Python style.
Raiders are rather ruthless characters who seem to actively seek out outsiders with the intent of ending their lives with no mercy. They do not obey any set rules nor laws and are rather brutal in their methods. They do often struggle with substance addictions and mental issues that make them less desirable/safe to be around. However, their lack of organization and scattered nature keep their numbers small and prevents them from becoming one of the biggest threats in the game. Regardless of that, steer clear of Raider home bases if at all possible.
5 The Forged
It is important to note that The Forged are a subsect of the Raider group; however, they have their own focus and motivation which differs from the group at large. Therefore, they have earned their own spot on this list. The Forged are rather brutal and show no mercy to outsiders nor members of their own organization and are known for the truly unfriendly ways that they greet those on their bad side. Avoid at all costs. They are not your friends. Their friends are not even their friends.
Gunners are highly trained mercenaries who use relatively sophisticated weapons and employ more finessed fighting styles than other enemies in the game. Gunners are known to be rather intense and will not hesitate to come after any player who is unlucky enough to cross their path. They also have armour, no substance abuse issues/dependency, and are organized enough to have established a defense system to protect their areas. Not the biggest threat in the game; however, it is usually best to avoid them.
Behemoths are uber powerful super mutants that are absurdly large. To add to their spooky nature, they can't speak at all. They just roar. That is it. It sounds silly but trust me, it is far less fun when they are charging at you. Way less fun. They can also respawn so avoid areas where they are known to pop up because they might be back for round two before you have even recovered from your last encounter. Though the plot does include direct interactions with the creatures, it is important to just avoid them when possible.
2 Mutant Hound
It is important to note that these creatures, who are rather brutal in their own right, also rarely ever appear in the game alone. They often act as the companion to other types of super mutants and the combination of the two is rather unpleasant, to put it mildly. They also tend to pursue in packs and can alert nearby hounds of the player's presence; summoning them to join their ranks. Avoid them, dispose of them quickly, and do everything that you can to avoid being bitten.
Oy, the Deathclaw. They are large and brutal creatures who have earned a reputation for being pieces of work in the Fallout fandom. They are difficult to take down for several reasons and should be avoided at all costs. They have a large health pool, pursue player's in groups/packs, inflict a lot of damage, and are incredibly fast (which can make it difficult to block and evade their movements.) They are the big bads of the Fallout world and my heart goes out to any player who has found themselves on the bad side of their species.