Season 1: BPL triangle (couldn't think of anything else lol)
Season 2: Besides the obvious one
Jeyton, Jules or how they wrote the Naley storyline.
Season 3: Same as before but Peyton & Pete storyline.
Season 4: Psycho Derek and point shaving stuff
Season 5: Lindsay/Peyton/Lucas and Nanny Carrie
Season 6: Mia/Chase and Mouth/Millie