Storm, Wolverine, and Nightcrawler facing off against Proteus circa Uncanny X-Men #127.
Cyclops battling Shaman's magic box conjurations with Sasquatch, Northstar, and Aurora waiting in the wings, circa Uncanny X-Men #121.
Kitty Pryde on her own trying to stay alive as a N'gari demon tears the mansion apart,
Uncanny X-Men #143.
Jean Grey's death scene with a horrified Cyclops helplessly witnessing, Uncanny X-Men #137.