The Soul Gem. Limitless manipulation of souls both alive and dead, also has shown to be able to evolve or devolve a beings physical self as well as their mental capacities. Ghost Rider. Who better to wield the Soul Gem than Marvel’s own Spirit of Vengeance?
The Time Gem. Allows the user total control over the past, present and future. Allows time travel, can age and de-age beings and also be used as a weapon by trapping enemies or entire universes in unending loops of time. Cable, arguably Marvel’s most popular time travelers,vet, with natural time travel abilities.
The Space Gem. Grants the user the ability to exist in any or all locations, move any object anywhere throughout reality and warp or rearrange space. Premiere member of the intergalactic police force known as the Nova Corps, Richard Rider is one of the few who could be trusted with the power of the Space Gem. And maybe then he wouldn’t have died trapped in the Cancerverse.
The Mind Gem: Allows the user to greatly strengthen and enhance mental and psionic power and access the thoughts and dreams of other beings. Taps the user into the universal consciousness, allowing for unlimited manipulation of psionic powers including telepathy and telekinesis. Hope Summers. One of the (very) few people who’ve been possessed by the Phoenix Force and managed to not only control it, but extinguish it.
The Reality Gem: Allows the user to locally or universally alters the natural laws of the universe to the wielders will. Already possessing reality altering powers herself, The Scarlet Witch might be one of the only people in the universe fit to possess the Reality Gem. And even though she’s frequently painted as unstable, I think she’d wield it well.
The Power Gem: Grants the user the power to access all power and energy that ever has or will exist, and can boost the other gems’ effects. Allows the user to duplicate almost any physical superhuman ability. Tamara Deveaux, The current wielder of the Captain Universe identity, was granted the immense power of the Uni-Power for the purpose of protecting universal balance. The Power Gem might tip the scales in the favor of the Captain.