Board Thread:General Discussion/@comment-35615238-20190608024117/@comment-38557913-20190610022156

Oofoofoofoofoofoofoofoof wrote: However, at least in the game, your ATK increases and your DEF decreases.

Undyne would be practically unbeatable if Frisk was LV 19 due to KR. Sans explains it when he teaches you about LOVE. The more LOVE you gain, the easier it is to hurt others (The reason most likely why Frisk does insane damage is their determination) and most  of the damage is reduced because... I forgot. Sans just says, "Ready?" and I die. Pretty sure Sans said your defense increases.