With so many villains focusing on long careers it's good to see someone who knows what he wants, goes for it and then gets out, and that plan would have worked perfectly for the Steel Slammer who was smart enough to avoid any of the typical superheroes. Even Iron Man, who would clearly have no chance against Steel which is clearly far superior to Iron, didn't find him.
What the Steel Slammer didn't count on was the rivarly of villains. His attempt to steal a single piece of priceless artwork was seen by The Green Goblin. The Green Goblin, showing his true civic mindedness chased down this villian who turned out to be a industrial spy.
He was presumibly going to explain how stealing a priceless work of art was spying rather than simple theft but the Green Goblin has seen the dangers of monologuing used this moment which is the downfall of so many villains to push the man in front of a train.
The first time villain was bounced between the train and several building but thanks to the absorbitive properties of Steel survived the battle and has remained out of the spotlight ever since.