I'll start:
Magneto
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Full control over the EM spectrum. By extension of the Unified Field Theory, able to control gravity, strong and weak forces as well
Can generate any form of radiation and light, including kryptonite (good for Superman) or yellow light (good for GLs).
Can create holograms of himself using light control and make himself invisible by bending light around himself
Can control any metallic object, no matter how small, including the iron in beings' blood. This gives him total control over an opponents body, allowing him to tear them apart or put them to sleep or shut off access to their powers
Can control minds using magnetic power and his own latent telepathy
Can see energy patterns and electrical impulses well enough to create and visualize CAT scans and nano-operate on others to modify their behavior or mental makeup
Can control all electrical impulses, including within the human nervous system. Can then destroy anything with a nervous system, as he did to two CL100 beings with power exceeding that of the Hulk
Can block psionic power with electrical fields, rendering telepaths and telekinetics useless
Was able to not only react to, but catch Northstar (99% lightspeed) mid-speedblitz after easily taking all of his blows
Able to generate forcefields capable of withstanding attacks from Galactus and the Phoenix Force
Can control matter at a sub-atomic level by destroying or creating bonds at the electron or proton level. At wide areas, can create atomic destablizing reactions that can cause spontaneous nuclear explosions in the atmosphere and can further the chain reaction to destroy the planet
According to Excalibur #12, does not actually need a body, similar to Iceman. So his body can be destroyed and he'll live as an energy being
Can reverse the polarity of the Earth, destroying it in the process
Can create wormholes and, by extension, blackholes with localized singularities
Can warp time and space to the point of time travel, time manipulation or teleportation
Can create a singularity of infinite mass so great that it collapses the universe
In proximity to Scarlet Witch, he can use her power to alter the multiverse to suit his whims. Or re-start it entirely with himself as Eternity.
Clearly Magneto at his full potential is the most powerful being in the universe.