2000 Alpha-plus level psykers from Warhammer 40k. Disperse them evenly throughout hell and unleash utter destruction. Satan would be my *****.
If those gundams showed up, they'd be set against one another instantaneously as the pilot's minds would snap from insanity and bloodlust. While the gundams may be able to move FTL, the pilots cannot. So once the gundams have battered themselves against each other, there will only be 1-2 left and in seriously damaged condition, and will be easy prey for those who can snap titans in half with a flick of their wrist.
Note: Alpha/Alpha-plus level psykers can do the following: 'An Alpha Plus, however, is a being of grotesque power. They are described in the 4th edition Rulebook as being able to "turn a man inside-out with a glance", "snap a Battle Titan in half with a flick of the wrist", and "a muttered syllable can turn an army upon itself in a frenzy of bloodlust". They are capable of destroying entire worlds - sometimes unintentionally.' (source: wikipedia)
Since I've already spread them out evenly all over hell, and assuming you have to be in hell to attack hell, as soon as anything shows up, it's screwed. As soon as anything shows up, just spawn kill it. If they don't kill it, they should set it up against its peers, resulting in a hilarious bout of friendly fire.
Alternatively, if the gundams become a problem, I could just wait for the pilots to leave the suits and them just poison them using one of the Dark Eldar's choices of horrible nastiness. They have to leave at some point and eat/drink/poop/etc. That's when you poison them. Then they die (in agony). Then the suits are useless without their pilots (unless they need no pilot, but then why would you have one in the first place if you didn't need one?). Hell would be mine.
