The Simian Avenger
The Simian Avenger was a superhero first created during the 1930s then resurrected in the 1960s by Millennium Comics. The book never sold very well and was discontinued after less than twenty issues. In the Millennium Comic universe, the character himself has continued but in a minor role (although he has his fans).
Essentially, The Simian Avenger was one of a group of animals used in a series of experiments by a supervillain named Dr. Morgue. He was attempting to create an army of super-gorillas under his direct control via mechanical implants. Most of the test subjects died horribly. All of them suffered. But one responding to the drug injections and surgeries by becoming highly intelligent. He and three other "successes" were presented to an assembly of criminals and foreign nationals, with the intention they bid on having more such "perfect soldiers" created. But the gorilla who would be called The Simian Avenger turned on them, killing Dr. Morgue and many of his "customers." He then dedicated his life to tracking down the kind of men who would commit this kind of atrocity.
Simian Avenger's powers centered around his augmented gorilla strength and flexibility. One of his eyes had been replaced, allowing him to cybernetically see in infrared or x-ray vision. He wore a power-suit that allowed him to fly and to emit force beams from gauntlets on his wrists. The Avenger was intelligent enough to repair and even augment his power-suit over time. Towards that end he got a side-kick/assistant name Tex, an inventor who also provided a home for the Avenger on a private island in Millennium City Harbor.
Interestingly, Doc Satan was originally created as a foe for The Simian Avenger--someone who could trade blows with the gorilla and survive. However, Doc Satan was always more successful than the hero he was designed to counter. Count Nocturno was also a regular enemy of the Simian Avenger.