While I will admit Eclipse and Aster are my favorite Meteors, my vote goes for Solaris.
This guy is indeed an interesting villian, to me anyway. What I do like about him, is that he doesn't doubt himself. He truly believes that what he does to Reborn and the people in it is the right thing. I've always liked this kind of villian more, because they feel more real.
One scene with him made me love him as a villian, which is the one where he tries to kill the MC. This proves that he early on knew that the MC was a threat (or an annoyance, as he calls us). I'm guessing that ever since that scene, he is still mad about Amaria saving the MC. He has destroyed Reborn, killed several people, but he has also failed to chrush that one little hope Reborn has: us, the MC.
Although I wish the battle inside Amarias home wasn't together with Florina, I still can live with it.