X-Men #168 - Paul Smith cover

X-Men v1 #168, 1983 - A battle-worn Kitty Pryde is backed up against the wall by an unknown assailant. 

 captures her exhaustion and determination at the same time. She's been featured solo on an X-Men cover once before, but this one (where she's literally spotlighted) is grittier and more compelling. Smith, who also drew the interiors, just joined the creative team and was already making his mark on the series.