Entities more powerful than IG, like LT, Lucifer, Michael, Toaa, GEB, Presence, HoTU, Beyonder,etc..
But with Cap's incredible fighting skills, tactical genius, and expert of battle strategy, could Cap possibly take out some of these people you mentioned with enough prep time?
It doesn't matter who wields the IG, the power is the same. And when you have full control over space, time, reality, etc... you don't really need prep or tactics, or fighting skills.
With such power, and a great strategical mind, Cap can find a way to warp reality or space or time in ways that could defeat beings such as Living Tribunal. I'm not sure what is and isn't possible with the Infinity Gauntlet. But let's say Cap created a wormhole in space/time that brought him back when LT was created. Cap uses the IG to somehow stop this creation, thus LT is never created. Is something like this possible? If so, Cap can defeat this person.
LT has immunity to such things. They just wouldn't work. It isn't about who has more skills, it's about who's more powerful overall.
Well I was in the US Army - two years in Iraq, Explosive Ordnance Disposal. In a fight, it doesn't matter who is more powerful overall. I engaged in hand-to-hand combat with a terrorist who was at least 5 inches taller than me and had at least 30 more pounds of muscle than me. He had a knife. I had my bare hands. But since I'm more skilled then him, I'm here typing this, while he is dead.