PvP Battles Are Still a Bit Confusing

It's hard to win when I'm using my maxed-out Lv. 200 characters against opponents with 3 stars or less and Lv. 180 or lower (ignoring status effect matchups), but when the opponent fields only Lv. 120-140 characters with no stars, my maxed-out Lv. 200 characters aren't struggling with status effects or instant death effects, they're just getting one-shot normally. What's going on? These kinds of players show up occasionally, and they're always so persistent and annoying...