In terms of sheer power, few can match the fully-loaded
Infinity Gauntlet.
The gauntlet's real power comes from the six Infinity Gems it carries.
The green Soul Gem allows the wielder to steal, alter, or otherwise manipulate souls. It's also a portal to an idyllic pocket universe that could, in essence, serve as a portable paradise. Essentially, it's control over life as we know it.
The orange Time Gem allows the wielder complete control over the past, present and future. The user can time travel, age or de-age beings at will, and even use time as a weapon by trapping enemies in never-ending time loops.
The purple Space Gem allows the wielder to be anywhere at once, or, if they choose,
everywhere at once. It allows complete control over the way objects occupy space, and can thus be used to move anything anywhere, or alter how space works (like altering the space inside a soda can to be the size of an Olympic swimming pool, for example).
The blue Mind Gem allows the wielder access to the thoughts and dreams of other living beings. Essentially turns the user into the most powerful telepath in existence.
The yellow Reality Gem allows the wielder to fulfill wishes, even if they directly contradict the laws of physics.
Finally, the red Power Gem allows the wielder access to all energy that has ever existed, or will ever exist. In addition to making the user superpowerful and invincible, it can be used in conjunction with other Gems to boost their effects.
In the wrong hands, this puppy has the potential to be
the most destructive weapon in existence. Of course, it's also got the potential to accomplish feats of goodness, but who wants that?