hmmmmmm I would say a trope I find really interesting to dig my teeth into is the evil one I used to be known for but I'll give a non evil answer and say exes to lovers. I'd say one that's been hard to write is enemies to friends to enemies to lovers which is what my long clexa fic is. I've learned from the comments that even when you think the mean acts between the leads are balanced, readers will view the POV character as in the right and the victim and it's hard to have real mean actions that both characters have to grow from while not completely alienating readers from investing in and rooting for the relationship.