The first Bulwark made his first appearance in Avengers #340. He was a human assassin.
This Bulwark was hired by Itzhak Berditchev, a man who, in his youth, was saved by Captain America from a concentration camp. Bulwark was highly trained in armed and unarmed combat, primarily using an electrified staff. He liked to call himself "The World's Deadliest Assassin." When Captain America invaded Itzhak Berditchev's estate, Bulwark fought him until he was defeated by Captain America.
Avengers #340 (10/1991)
The second Bulwark made his first appearance in Generation X #11. He was a German mutant named Oswald Boeglin.
This Bulwark was recruited by Emplate to join his team (called in advertising as Hellions) in attacking Generation X in his various bids to recapture Penance. Later, he met his end when Weapon X captured and gassed him at Neverland. He possessed the ability to turn from a scrawny guy into a hulk by expanding his muscle mass, increasing his strength, durability, and resistance to injury to supernatural levels.
Generation X #12-14
Weapon X #5
The only thing the two Bulwarks seem to have in common is that they were both created by Scott Lobdell. Maybe he liked the name and decided to reuse it.