No one said Prince of Death with 9/10 dominion? That's my favourite. It can expand since turn 0 and archers/javelins alone pose a problem for him.
Forge him armour/helmet/shield and no indy can touch him. Also a move of three via air. Can always attack rear. And can kill pretty much most normal armies that are not supported by high researched mages or SCs. Can also single-handedly take all underwater provinces with a ring of water breathing or a similiar item - a nice bonus in a game where there are no underwater nations.
Basically I seem to love it.
Oh, and I've never lost arena with him yet. This gives nice exp boost and a trident which makes him all the more lethal (actually kills stuff instead of making everything flee
. Yup I'm aware some SCs would kick his *** in the arena, but just haven't ran into those yet.