Yes , he becomes strong but not all of sudden to challenge the monsters at top or Rankers that climbed to the top but in his own level he is the strongest , the more he climbs the more he gets strong , it gives shivers the rankers when they spar/fight him because his potential is scary and monster . the first part of the story is about world building and character growth but the second part where everything changes and he get betrayed , just read it man , it is awesome , I've read it quite a lot of times .

1. He isn't betrayed by a friend, but by a classmate who bullied him (though I don't think he knows who betrayed him).
2. When his classmate betrays him, everyone thought he died and so he was separated from his class and didn't rejoin them.
3. He's not exactly evil, but he's not good, and he does (plan to) indirectly go against the "good guys" that his classmates are a part of.
4. I've never seen a protagonist colder than him.
5. Although he starts out powerless and even gets bullied, after a few chapters he gets betrayed and then gets pretty powerful, and then insanely over powered pretty quick, and he doesn't hesitate to use that power when he needs to.

1. not only betrayed by his best friend but he was sacrificed to the demons.
2. swear vengeage, leave everyone from his past and start hunting demon and human who humans who have made a deal with demons
3. had an armor which made him bat shit crazy evil and start raping anything that move with his big long sword :D
4. Crybaby?? Gatts is the definition of testoteron raging freak
5. he kill hundreds men in one battle, have cannon in his hand and also fireproof

1.) Protagonist was abandon by his family for not being able to use the power of fire.
2.) Protagonist left and what he did while he was gone is unknown.
3.) After some time he return with the power of the wind and is super OP
4.) However, he resent his family for abandoning him and acts like a jerk.
5.) He's cold and arrogant.