Many players have a preference of which Killers they prefer to play against. Every time Survivors spawn in one of The Entity's trials, it's a total gamble as to which Killer will be on the prowl. That knowledge alone instills a sense of dread in Survivors, but while certain Killers present a welcome challenge, others can be plain infuriating.
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Even some of the more popular Killers have quirks about them that make it hard to fully appreciate them as legendary licensed characters or well-designed original characters. It can ruin the mood to realize that one of the more tedious Killers will be making the Survivors' lives a misery for the duration of the Trial. Every Dead by Daylight player has their preferences, but there are some Killers that seem to cause everyone trouble.
While The Knight exists as a fascinating concept, the character gets a lot of hate for being a "no skill" Killer who often utilizes the use of guards to obtain free hits and hook-camp. Although camping and tunneling aren't illegal, it is frowned-upon by the Dead by Daylight community as a show of poor sportsmanship by targeting certain Survivors.
For The Knight, one popular tactic involves hooking a Survivor and deploying a ghost-guard to camp the hook and make it almost impossible for Survivors to retrieve one another unless they are completely healthy and can afford to inevitably take the hit. However, the hunt ends automatically when the Survivor is unhooked, so it isn't ultimately as effective as it seems. Still, The Knight makes for a frustrating opponent.
Perhaps one of the Trickster's more unforgiving qualities is the fact that—in general—he's not very exciting to play against. This is no fault of Behaviour Interactive's (his design is fantastic), but Survivors have to counter him by running very tight rock formations, trying to duck under high walls, or getting lucky by running him around labyrinthine structures with plenty of obstacles to block his knives.

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Playing against The Trickster feels repetitive, which can make it annoying to play against him, as there's hardly any stimulation compared to more complex Killers like The Pig, whose gameplay is more interactive for Survivors. It's ridiculously hard to avoid being pummeled by the Trickster's knives, which tends to suck the fun out of playing against him and makes him one of the more irritating opponents.
As the first licensed Killer to be added to Dead by Daylight, Michael Myers' popularity has waned over the years—as expected—due to the number of new Killers that have since become available. He will always be one of the greats as far as slasher villains are concerned, but he isn't without flaws. Michael is one of the more exciting Killers to play against, but he's also extremely frustrating for one particular reason: Tombstone. Unfortunately, the add-on Tombstone Piece makes Michael extremely annoying.
Once he reaches Tier 3, he can Mori the Survivors mid-game without any hook states. This kills them instantly if they get caught and results in very short, very tedious matches. As a base Killer, Michael is a pure delight to see, especially since he isn't played much anymore. However, running Tombstone on Michael certainly takes the appeal away relatively fast.
Before he got buffed, Freddy Krueger was one of the weaker and underutilized Killers, but ever since Behaviour went and reworked him, Freddy has become a more challenging foe. Unfortunately, that also makes him infinitely more annoying. From a Killer's perspective, Freddy has no anti-loop mechanics, such as how long-range Killers can hit Survivors across windows and pallets. He has no real mobility, either.
That being said, Freddy received a buff recently that now allows him to place Dream Snares and Dream Pallets at will, as well as teleport to Survivors who are healing and repairing. For this reason, he has become one of the biggest nuisances, mainly for his teleportation ability, which gives him far too much map mobility.
First and foremost, one of the most heartbreaking realizations when playing against The Plague—which also happens to be deeply upsetting—is bringing a med-kit against a Killer whose power prevents Survivors from conventionally healing. It's easy to feel as if a whole item was wasted. Normally, matches against The Plague run on for a ridiculously long time, and most Survivors want to take their win and move on (or their loss, if that's the outcome) rather than dragging out a game that has a clear outcome.

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Since The Plague's power forces Survivors to waste time cleansing, they aren't as focused on generators, which slows the progression of the match right down. Playing against The Plague means that Survivors are constantly one hit away from being downed, so that's never any fun.
When facing The Cenobite, it helps to have at least one Survivor on "box" duty, which is delegated to one individual to prevent Pinhead's chains from hindering healing, repairing, and running. If there's no one on "box" duty, the match can be considered a loss from the get-go, as that is how Pinhead gets most of his leverage. His chains can interfere when Survivors jump on generators, when they try to heal, and when they try to solve the box after the fact.
In that case, Survivors will be constantly pulled out of the action and oftentimes even forced to start over. If a Survivor is snagged by a chain while solving the box, the progress will reset. This can make Pinhead very tedious to play against, even if he does have one of the cooler skill-sets of the Dead by Daylight roster.
Leatherface has garnered a reputation as one of the worst camping and tunneling Killers in Dead by Daylight. Generally speaking, playing against Leatherface ends in one of two ways: either Leatherface hook-camps one Survivor to secure one kill and their teammates leave them, or the more selfless teammates go back to unhook them and Leatherface downs them all for a four-K. The fact that Leatherface can insta-down Survivors is another huge factor, as it give Survivors a very limited window to avoid a quick hook.
Not just single Survivors, either. Leatherface can down the whole team, potentially, in just one power usage, whereas other Killers who can insta-down at least have a significant cooldown. Besides that, he makes sounds (especially when he revs the chainsaw) that are grating on the ears, so it gets annoying relatively fast. His chainsaw sweep is not only too swift to counter sometimes, but it also lasts long enough that it's near-impossible to run from.
Good Nurses are notoriously difficult to dodge, which is something that anyone who has played against a seasoned Nurse main can attest to. The Nurse is one of the few Dead by Daylight Killers whose only real limitation is the skill level of the person playing her. She can be hard to counter, especially if someone knows what they're doing and utilizes her Blink power effectively. Trying to juke a Nurse doesn't usually end well; plus, she regains her Blink so fast that creating some distance still doesn't feel like enough.

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From a Survivor's perspective, she can be annoying because she never stops coming, no matter what Survivors throw at her. She's arguably the hardest Killer to avoid, especially once she commits to someone, and that can be exasperating for Survivors who have no real way of avoiding a hit. There's the option to use Dead Hard, but without it, Survivors can feel miserable going against her.
Just like Bubba, one of The Doctor's biggest drawbacks involves the sound effects he makes. Not only are they loud and obnoxious, but combined with his static, Survivors can get real-life headaches. There's too much stimulation when The Doctor uses his powers, which isn't only distracting but also a variable that isn't accounted for as far as the expectation for video games to influence life.
The constant noise that The Doctor emits makes it hard to concentrate against him, but it also has a negative effect on anyone who struggles with overstimulation, similarly to Clown's motion sickness and Plague's vomit. Plus, it's annoying to reach the highest level of madness and be unable to perform any action until the Survivor "snaps out of it," as it wrenches control away from the player.
Legion is one of the best Killers in the game, objectively, but also one of the most irritating. When playing against The Legion, it's expected that Killers will deploy the tactic of running around in Frenzy and swiping Survivors to keep them injured. Oftentimes, a Legion won't even down anyone until halfway through the match. They will just continuously keep Survivors injured and needing to mend. While a lot of Legions likely do this to corral Survivors and also farm Bloodpoints, it's a tactic that gets pretty old.
When Legions are in frenzy, it triggers a painful back and forth between getting injured, healing, and getting injured again. It makes the matches drag on forever, which creates the same argument as Plague. Games against Legion can be dull, which is the one thing that no video game ever wants to be, as players lose interest quickly.