The mutant Forge is mostly only used as a minor character. However, his power allows him to create any device he imagines in his head. Forge has proven himself capable of creating the most incredible inventions. And he could very well create a device capable of destroying the universe. Of course, if he ever got that into his head.
2. Sister Grimm.
The hereditary sorceress Nico Minoru, also known as Sister Grimm, has magical powers and can summon the mighty Staff of One. Nico has demonstrated her powers and the power of the staff many times. The sorceress' destructive potential is not fully understood. However, she could very well summon some kind of spell capable of destroying the universe.
3. Dark Phoenix.
The destructive power of the Dark Phoenix destroys everything in its path once it finds a host. As the Dark Phoenix, Jean Grey sacrificed herself to save the world. If not for her sacrifice, who knows where things would have gone.
Cyborg Michael Korvak, a cyborg who absorbed space power from Galactus' ship, is able to manipulate reality and could easily cause the destruction of the universe.
5. Mr. Fantastic.
Reed Richards has an ingenious intellect, creating various inventions. And sometimes these inventions do more harm than good. Reed Richards is capable of creating technology that will lead to the destruction of the universe.
6. Molecular Man.
Molecular Man has control over matter and energy on all levels. He is a multiversal composite entity. And the death of one of his versions led to the destruction of the universe in which that version was located.
The otherworldly possesses godlike power that allows him to change reality. The otherworlder has such powerful power that he created a planet that he filled with heroes and villains to observe the confrontation of good and evil.
8. Franklin Richards.
Franklin Richards possesses an array of powerful abilities. And in the future, he is destined to become so powerful that Galactus will act as his messenger.
9. Scarlet Witch.
The Scarlet Witch has enormous power, which has already allowed her to wipe out some of the Marvel characters as if they never existed.
10. The Almighty.
The creator of the "Marvel" cartoon universe has infinite power. And he is capable of destroying the entire multiverse, just as he created it.