|I second Tower of God .
And about that powerful question
Spoiler (mouse over to view)
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 .