Necros are okay if it's still a relevant subject.
As for the worst card in the game, I'm gonna have to say Diego. Most cards have SOMETHING going for them – Ogoun Kyu can block damage from cards like SkrumxxT, Bob Joby can sneak in that magical 6 damage with enough luck and Globumn actually stands a chance in low pill battles.
But Diego is just crap in all situations lol.
If you ask me, I thought Robin (Sentinel) at first was the worst card, that is until I saw he has an ability of "Power +2", then I though, "Okay, so he must be kind of like Cell (Nightmare). Reliant on Damage, but not power. Cards like Krash (Rescue) are the other way around from what I recall." But Boostr really hit an all-time low with Nobrocybix (Junkz). Seriosuly, 2-Star Max? 1 Power at Max Level? 5 Damage at Max? No Ability? What were you thinking Boostr?! It's like the ONLY way you can win a round with this guy is the clan bonus (and wasting all of your Pillz). Even in NoPillz! So if you're thinking about buying cards in the market, save your Clintz, people. There's something more worth buying with your Clintz than this worthless card.