Since there are no canon pairings that I hate (there aren’t that many anyway), I’ll list two non-canon pairings that I ABSOLUTELY DISLIKE.
Finn and Princess Bubblegum. Sorry, but PB has pretty much stated on a few occasions that she doesn’t like Finn in that way. I see their relationship as more of good friends and or even almost sibling-like. And by the way, Finn is fucking fourteen, so stop it. Unless you’re going to pair them at the same age, just…please no.
Finn and Marceline. Let’s be honest here. These two have a lot in common. They both love doing crazy cool things with each other and also like to have jam sessions. But, like Princess Bubblegum, Marceline has also stated that she has no interest in dating Finn. And by the way, Finn is fucking fourteen so can you please stop pairing him with these two unless he’s older?!