RE: worst card in pokemon tcg
By default, Pokémon Star suck. Really. I tried using Latios Star once. He hit one guy and then got his face rocked. If this topic was called "worst pokemon star in pokemon tcg" we'd have a pretty good discussion since they're all pretty much terrible.
On topic, my vote goes to Base Set Gastly. 30 HP, can never do damage. Sleeping Gas means 25% chance of them still being Asleep by the time it's your turn again for your evolution into Base Set Haunter and do 50 for 20. You rule.
Or you could use Destiny Bond and get rid of you energy. Then you can smirk at the thought of Gastly taking down your big Pokémon-ex. Oops! I just said go. There goes your attack. Keep on attaching and doing Destiny Bond, I'll just keep right on healing and saying go until you deck yourself.
If that's not bad enough for you, how about Ancient Technical Machine Steel? Seriously, I can't think of a REAL use for this card. The only situation I can even consider this to be useful is if the Defending was poisoned with 10 HP left and they had Energy on anyone on the Bench. Steel Generator, Defending dies, there goes its Energy +2.
But that's it. What a stupid card.