VII - Palmer. Well he is a joke boss.
VIII - Sphinxaur/Sphinxara. Though since you can only Attack, they really couldn't have made him a harder boss without potentially ruining the game.
IX - Zorn and Thorn. They literally cannot hurt you if you know what to do.
X - Seymour Omnis. Hooray for Nul-spells.
X-2 - Shiva. There's really not much to her.
XII - Slyt (the Water fish guy in Pharos). Weak to Fire, vulnerable to Oil. Nuff said.
XIII - Barthandelus III. Though the bosses after him made up for that.
XIII-2 - Noel vs Caius solo fight. Surprisingly simple, especially after the somewhat challenging Serah + Monster vs Caius fight.