Kevin Leonardo is the third person to be called the Atom Smasher.
The third Atom-Smasher was unrelated to the first two. Named Kevin Leonardo, he was a whistle-blower against Stane International, causing them to retaliate. He was shot and put in a radioactive canister. He gained powers and searched for revenge. He attacked, fought, and defeated James Rhodes who at that time, was using the Iron Man armor. Later they both fought Firepower. Eventually Rhodes let Atom-Smasher leave in peace.