A flurry of first kills in Naxx 25, here they are, Abom wing and then Frost Wyrm wing coming up soon.

Spider Wing

Anub'Rhekan

Grand Widow Faerlina

Maexxna

Plague Wing

Noth the Plaguebringer

Heigan the Unclean

Loatheb

Death Knight Wing

Instructor Razuvious

Gothik the Harvester

The Four Horsemen