The Quintronic Man was a project in which professor Burke was working under the command of A.I.M. based from Iron Man. It’s an exoskeleton which needed 5 men to operate, including himself. But Burke, the key agent on the project left A.I.M. before it was finished.
Colin Thirty-Three sent two agents to kidnap professor Burke, in a apparently failed attempt to prevent A.I.M. mission from success, S.H.I.E.L.D. managed to change a face-covered professor Burke with Bruce Banner, who as soon as he entered A.I.M.’s facility, started causing havoc.
Colin decided that the project could’ve been finished without Burke, and used another A.I.M. agent to cover Burke’s place. Other S.H.I.E.L.D. agents who supported Hulk were defenseless until the hero crashed on the scene. The Quintronic Man tried to kill Hulk using the lava of the volcano the A.I.M. base was in, but he survived, and crashed the suit’s protection, allowing the lava to reach Thirty-Three and the other four agents, killing them and destroying the suit.
Source: Marvel Wikia
From: Incredible Hulk #213 (1977)