Aki

Tragic
Ohh man, I finished reading Chainsaw Man part 1 in a day and it left me staring at my bedroom ceiling for a good 10 minutes. Aki is a "revenge" character done correctly, the character development he goes through is crazyyy. He's a way better character than Sasuke. He starts off looking for the devil who wiped out his family and chooses to exchange years of his life for power. Unfortunately he realises no matter how much power he gains, he'll never be able to carry out his revenge (the Gun Devil is disgustingly OP). Aki accepts this fact, gives up on his revenge and decides to focus on his "new" family (Denji and Power). This is short lived because he falls to the very same thing that took his family. What I like about him the most is what he represents in the series, The realisation that devil hunters die young and there's not always a good ending to a revenge story. Rest up the best character in CSM.
Personality

Cool, calm and collected, Aki was the most mature hunter long before he met Denji and Power. Over the course of the series, you realise the cold approach he shows is a front. He cried over Himeno’s death (RIP, she was cool), saved Angel despite being a devil and eventually considered Power and Denji family. CSM mentions a few times that compared to other devil hunters, Aki is considered “normal”. I knew this wasn’t a good sign once they emphasise how the more “normal” a hunter is the more likely they’re are going to die young. Denji and Power are crazy af so it makes sense why they both outlived Aki.
Just like any normal person grieving, you tend to make emotional and illogical decisions. Aki does this several times because he doesn’t want to lose anyone else. After going through various circumstances, his life span is cut down to 2 years. He puts personal feelings before the mission. I like to think if he was more like Denji and power (more crazy) he would definitely have lived a lot longer. He went from despising devils to risking his life for them, peak character development (for a shonen character).
You cant blame him for having the “Us or Them” mentality.
Abilities

Lemme break this down. In Chainsaw Man, devil hunters hunt devils through contracts (kinda like the “Deal with the Devil” thing). A hunter goes up to a devil and offers up something valuable to them, in exchange they would then be able to use abilities that devil has. In Aki’s case he made 3 contracts with 3 different devils:
Fox devil: Feeding part of his body to it allows him to summon its head and choose a target for it to bite down and swallow. Lets be real here, this is the coolest one compared to the other two I’m about to mention. The voice actress for the fox in anime was top notch, I wish the devil lasted longer tbh.
Curse devil: After making this contract, Aki gains a sword that summons the curse devil to deal massive damage after the target has been hit with it 3 times. I’m gonna be honest, this devil was a disappointment. It took a chunk of Aki’s lifespan and didn’t make much of a difference when Aki used it against Katana Man. Not a fan.

Smoke
7/10, When it comes to protecting those he cares about, he’s on devil timing. He started off not hesitating to send devils back to hell but over the course of the series he grew a soft spot for some of them. To put it shortly he discriminates against devils heavily (excluding his few devil friends).