There's a real debate about what makes a truly successful omnipotent soldier character. If they can just blast through everything with zero effort, that's boring. The best examples I've seen show success through what the power costs them. In 'Ender's Game', Ender's strategic genius wins every battle, but the psychological toll is the real challenge—he's successful militarily but broken by it. The success is hollow, which is the point.
Another angle is when their omnipotence creates new problems. A character who can't be hurt might become detached, or their power makes them a target for political manipulation. Success is shown when they navigate those non-physical threats, using their power in clever, restrained ways rather than just overwhelming force. I think that's more interesting than another fight scene where they obviously win.
Sometimes the challenge is self-imposed, like holding back to protect others or follow a moral code. Watching a character succeed within those strict, personal limits shows a deeper kind of strength. That's when an omnipotent soldier stops being a power fantasy and becomes someone you can actually root for.