Minor spoilers for Incredibles 2 to follow. Incredibles 2 is finally here, and that means the Parr family is back to fight crime once more. There's Elastigirl, who can stretch her body like rubber; Mr. Incredible, who's incredibly strong and resilient; Violet, who can turn invisible and create force fields; and Dash, who possesses superhuman speed. And then there's baby Jack-Jack, who... wait, what are Jack-Jack's powers? The baby's powers don't manifest in The Incredibles until near the end of the film, and it's never made clear exactly what he can do. Thankfully, though, Incredibles 2 sheds some more light on the abilities of this super baby.
In Incredibles 2, Jack-Jack is revealed to be a polymorph, meaning that while some babies are born with several superpowers, Jack-Jack seems to have been born with all the superpowers. The film doesn't really set a limit on what he can or can't do, but it does show him performing a number of superhuman feats, including but not limited to: shooting lasers from his eyes; shape-shifting into a demonic, Hulk-like beast; walking through walls; levitating; teleporting to other dimensions; producing lightning; breathing fire; creating multiples of himself; and becoming, for lack of a better term, a human torch.
Although Jack-Jack is unique to the universe of The Incredibles, he isn't the only supremely powerful baby in all of superhero fiction. One likely influence on the Parr family from the start has been Marvel's first family, the Fantastic Four, according to Digital Spy's Simon Reynolds, and they have their own super baby who may have been an influence in the creation of Jack-Jack. Debuting in 1961, one year before The Incredibles takes place, the Fantastic Four was originally made up of Mr. Fantastic, the Invisible Woman, the Human Torch, and the Thing. Mr. Fantastic — whose name clearly inspired Mr. Incredible, and whose powers of elasticity are mimicked exactly by Elastigirl — eventually marries the Invisible Woman — who can turn invisible and project force fields just like Violet — and in 1968 they have a son named Franklin Richards.
While Franklin's parents received their powers due to cosmic radiation exposure during a space mission gone awry, he was born superhuman, making him a mutant in the Marvel Universe. And although he doesn't possess every superpower like Jack-Jack, even as a baby it becomes clear that Franklin Richards is tremendously powerful. As in, one of the most powerful beings in the multiverse powerful.
Franklin's powers can be broken down into two main categories. First are his psionic powers, which give him the ability to control minds, communicate telepathically, move things telekinetically, and see into the future. Those powers alone would make him ridiculously powerful, but he also possesses reality warping powers that are basically superior to those of anyone else in the Marvel Universe. He can can control all matter and energy at will, and has the ability to essentially create anything he wants and reshape reality as he sees fit. So even though he doesn't technically possess "all powers" like Jack-Jack, his reality-altering powers would essentially allow him to gain whatever power he wanted. He once even created his own universe from scratch, according to i09's Rob Bricken. Let's see Jack-Jack do that.
Jack-Jack probably isn't quite as powerful as Franklin Richards, who may or may not have influenced his creation, but there's still no shame in his game. He can do anything a superhero can do in the world of the Incredibles, and that should be enough to make him the most powerful being in his universe. Well, once he grows up and learns how to control his abilities, that is.