[LightningZERO]

I think Setsuna, Lockon and Allelujah/Hallelujah merged are pretty close in term of skill, they all managed to pull off quite impressive moves sometimes (Setsuna in the final episode, Lockon when fighting Ali, and Doublelujah against Soman and Sergei).

I'm certain that Tieria is the weakest. His style is just stand there and blasts things. I guess piloting a heavy armed MS will make you lazy