Complex sentence: Cockrum was a prolific and inventive costume designer who updated the uniforms of the Legion of Super-Heroes and did the same for the new X-Men and many of their antagonists in the 1970s and early 1980s.
Split into simpler sentences: Cockrum was a prolific and inventive costume designer who updated the uniforms of the Legion of Super-Heroes. He did the same for the new X-Men and many of their antagonists in the 1970s and early 1980s.