Complex sentence: When he first began his criminal career, it was revealed that Blue Streak was served as an operative of the Corporation who wanted him to infiltrate S.H.I.E.L.D. S.H.I.E.L.D. later decided to put together their own group of Super-Agents, and Blue Streak became a member of that group.
Split into simpler sentences: When he first began his criminal career, it was revealed that Blue Streak was served as an operative of the Corporation who wanted him to infiltrate SHIELD. SHIELD later decided to put together their own group of Super-Agents, and Blue Streak became a member of that group.