Endeavor is the number two hero in Japan and Shoto Todoroki's father. He is a fierce combatant with a drive to be the number one hero. His quirk is Hellfire and it allows him to generate and control flames.
Endeavor has a free Enhance that gives his non-Throw attack plus one damage for every six cards in his discard pile. This means the longer the game goes on, the harder his attacks will be hitting. Just don't wait too long or your flames will extinguish once you cycle your deck.
Endeavor's second ability is a Response that requires him to commit. It triggers when Endeavor takes 5 or more damage and let's him add one attack from your discard pile to your hand. This ability is great for getting the perfect block or for crafting your hand for a counter attack if your rival fails to defeat you on their turn.
This version of Endeavor is all about making his attacks stronger and his rival's attacks weaker. This isn't done freely though, he pays a very real cost as he tries to pursue that number one hero spot.
Endeavor's first ability is an Enhance that requires him to lose one health. Then his attack gets plus two speed or plus two damage. If his rival holds onto block, then he can add speed to make his rival have a harder time blocking. If his rival plays out all their cards, then he can add two damage to his attacks to make them pay the price.
His next two abilities are only playable once per turn and require him to lose two health as a cost. One of the abilities gives his Rival's attack minus four speed and the other gives his Rival's attack minus four damage. Both of these are incredibly strong abilities. Minus four speed means Endeavor will block an attack if he wants to. While minus four damage means some attacks he doesn't have to block at all because he can reduce the attacks damage to zero or less.