My least favorite is definitely the Buu Saga.
It started off decent with Gohan going to school, Krillin having a family, the rest of the characters having moved on, and the tournament. After that though it just got kinda lame to me
Everybody who wasn't a Saiyan was pretty much obsolete. Not even Piccolo was considered a legit contender by that point.
After Gotenks, Vegito, and Mystic Gohan are all each touted as the only way to beat Buu, none of them accomplish much of anything and Goku ends up beating him with a move he learned in the Saiyan Saga. In his base form.
Goten and Trunks going Super Saiyan at eight years old?
Vegeta's death on Namek >>>>>>>> Vegeta's final sacrifice against Buu. That whole saga never would have happened if he hadn't sould his soul in the first place.
Not a popular opinion, but I honestly don't mind the Garlic Jr. Saga. Yeah, he's a corny villain, but it was a breath of fresh air seeing the rest of the characters actually saving the day without Goku or Vegeta for once. We see Gohan saving the day, foreshadowing his role in the Cell arc. We get to see Piccolo shining. We see Krillin pushing the flyest whips and rocking the cleanest suits, and we get a glimpse into his love life. We see Vegeta in space searching for the secret to going Super Saiyan. I admit it isn't amazing, but I still like the Garlic Jr. Saga. It's a real shame Tien never showed up in that arc.