Geist Geld - Two successful attacks
BitcoinExpress claims one attack. The first was ArtForZ's. ArtForZ has claimed in public IRC channels that there is no evidence that BitcoinExpress did what he claims on the GG chain so the claim of even one sucessful attack here is dubious.
Fairbrix -Reorged the chain and stole over 1700 blocks.
There is no proof this was BitcoinExpress. He should move coins around if he wants to prove it was him.
Namecoin - Rumored to have paid off by NMC Dev not to attack
Rumours don't mean anything. I know of no one paying him off for the attack.
Solidcoin 1 - Scared CH so bad he killed the chain as a precaution after seeing GG hit.
This one I don't know about.
I0C and IXC - Numerous test for 51%, basically killed them
Where is there evidence of tests for 51% attacks on these coins by BitcoinExpress?
Bitparking - Number 1 suspect in DS attack has every trait of BCX
Again, no evidence it was BitcoinExpress. He can prove it by moving the coins out of the I0Coin address holding the double spent coins - by posting in advance the amount he plans to move.
Basically he may or may not have done any of the above. There's no proof either way.