I think the Expendable is the strongest one in the group, which was a complete accident on my part considering I overlooked it in his creation.
He could summon minions and then Deathgrip, leaving someone to die a slow and painful death at the hands of angry flora. He'd only use it as like a completely last-ditch method, but that's pretty strong all things considered.
I designed him as a support character, offering backup in his summons to keep someone safe or keeping the enemy held down for heavy damage from his allies while he kept the enemy held down using Deathgrip, and the obvious thing is his blood healing as a way to act as a medic for this team. Now that I've seen this true potential from him, I think he's the most definitive force of power on this team.
Again, his slow and painful killing will be a last ditch effort to actually kill something, so it'll hopefully never happen, unless anyone wants to try and kill him right now, in which case I hope you can kill his minions while having no access to any movement.