Honestly, deathly Hallows. At this point too many flaws in JKRs writing come to light. We spend a majority of the time needlessly in the woods, we get the flashback into Snapes totally not censored memory and never focus on interesting parts of the story. Honestly, 90% of the success the trio has in DH is from sheer and dumb luck
Btw, I find Lavender Brown rather annoying, so whichever book she simped over Ron in is my least fave, but I don't recall which one that was lol, someone pls tell me! xD