The phrase "big dude" typically refers to a large and strong person, usually a man. It is often used informally to describe someone who is physically imposing or has a large build. Full definition
As seen below, the main cast is diversely populated with ninjas, sword wielders, big dudes with big guns, magic users, guns wielders, a talking cat, and even a stuffed animal! (retrogameman.com)
We don't have a problem with that, mind you, since it means big dudes doing big things and that's our whole thing. (sbnation.com)
Simply put, Bile Trolls vomit and regenerate health, Spawn of Chaos have a tentacle arm, Rat Ogres are big dudes who knock you around, and Stomrfiends are Rat Ogres with flamethrowers. (thatvideogameblog.com)