Your anime is only as good as its funniest character.
Comedic relief characters are very common in anime of all genres. Even horror anime can have a comedic relief character. Let's take a look at a few.
5. Megumi from Shiki
Shiki, despite being horror, has a lot of comedic relief, which is applied carefully, so that tragedies do not appear funny. To be clear, Megumi is only treated as comedic relief before she falls deadly ill. Shiki initially has a rather slow pace, and in the beginning, there is space for youngsters being youngsters and hating the old village they are stuck in. For the first handful of minutes, we are invited to find Megumi funny.
4. Excalibur from Soul Eater
Excalibur is more of a menace than anything else; many people find him annoying, but he is definitively a designated comedic relief character. He is an apparently extremely powerful sentient sword. He is also a universally compatible weapon, which makes him suitable for anyone. However, because of his irritating personality few can wield him, and the main characters decide he is too much of a hassle to try and use.
3. Team Rocket from Pokémon
Despite technically being antagonists, Team Rocket are also very, very funny. They always lose and are bad at almost everything they try, including villainy and disguises. They are essentially comedic relief, which is why they get on this list.
2. Slime from Ragna Crimson
Slime in Ragna Crimson serves Crimson, a truly horrific creature, but Slime's personality is very different from that of its master. To be clear, Slime is horrible in its own ways; it eats dead bodies, after all; but it is meant to be cute, and so far, it is succeeding. As a result, when Slime is threatening someone, it looks funny more than threatening, and that makes Slime a cute comedic relief character.
1. Zenitsu from Demon Slayer
Zenitsu's main character trait is being cowardly, and it is played up for laughs. Not everyone enjoys laughing at a character for being afraid. Besides, demons are scary indeed, are they not? But Zenitsu's reactions are exaggerated to the point where it is difficult not to laugh.
Overall, comedic relief characters appear in all kinds of anime, from horror to adventure. They are meant to entertain, and some of them manage to do it, making them memorable and beloved. Sometimes, though, they are more of a bother. Naturally, only you can tell which comedic relief you enjoy and which you do not; it is subjective. That is why this list is only an example of comedic relief that you might enjoy.