Actually, Klaus is 2x19:)

she shouldn't have come back at all

I agree with "Klaus" but I like a lot 2x09 and 2x11!

2x18 is The Last Dance. I liked both 2x18 and 2x19 (Klaus) anyway :D By The Light Of The Moon was bad, but the Forwood scenes saved it for me. And I liked Katerina. Plan B, not so much...

The only good thing about Katerina was Katherine, but every other scene/story line was boring.

I don't know why but I loved Plan B, I thought it had some great scenes in there like Stefan/Elena break up (beautifully acted by PW and NB) and Caroline/Liz scene (again amazingly acted by CA)

By The Light Of The Moon was pretty good. Tyler and Caroline were amazing, and everything else was kind of boring though (much like Katerina)

I don't know whether you mean Klaus (2x19) or The Last Dance (2x18), but if you're talking about The Last Dance then I totally agree. That episode was weak and anti climatic for me, also it was really overrated and over hyped in my opinion. However I LOVED the episode Klaus (2x19)

a bit boring.

Found this one a bit boring..

2x11 was SOO bad in my opinion.