In X2, which mutant attacks the White House at the beginning of the film?

In X2, the mutant who attacks the White House at the beginning of the film is Nightcrawler.

Nightcrawler infiltrates the heavily guarded presidential residence in a spectacular opening sequence. He uses his teleportation ability to move through the building, leaving blue smoke behind, before being wounded and escaping. The attack prompts the U.S. government to intensify its response to mutants.

The character is later identified as Kurt Wagner, a German mutant with blue skin, a prehensile tail, and teleportation powers. Alan Cumming played Nightcrawler in X2, which was released in 2003 and directed by Bryan Singer.

Nightcrawler’s opening attack is not presented as part of Magneto’s plan. The film later reveals that Colonel William Stryker manipulated events to target Professor Xavier and the mutant population. Nightcrawler returned in X-Men: Apocalypse, where Kodi Smit-McPhee played a younger version of the character.