Redeemed antagonists who are/were high-ranking warriors (O'Chunks was an army general and Undyne is the leader of the Royal Guard) from unique RPG games who work for the tragic and supposed big bad of their game (Asgore and Count Bleck) whom they are very loyal to. They pop up a few times to face against the protagonist in their quest to stop their boss, but they ultimately were defeated (multiple times in O'Chunks' case), later having a change of heart and no longer act hostile towards the hero.

Also I kinda wanted to add the connection that both were humiliated after being defeated but not sure if this applies in the context of Undyne vs Frisk, although I guess it still counts since Undyne was said to be humiliated when she couldn't land a hit on Asgore and O'Chunks... Well, y'know. Take this "connection" with a grain of salt though.

Do both have better? Yes. Do I still like this? Also yes.