Well a full Combo is roughly as strong as the Greeed would be with all his, or her medals. And going by the PokÃ©mon rule, same type Vs. same type is not very effective. Meaning both parts will be knocked down a notch. Though It's kinda wierd, in episode 31 Eiji asks for a combo strong against Uva, he gets TaJaDor. So I think it's like this in terms of their elements; Ankh -> Uva -> Gamel -> Kazari -> Mezool -> Ankh. And the Purple Greeed is probably stronger than all of them.