Kill the Justice League... as a D&D character

[Zagreus]

A neigh omnipotent being is bored and decides to kill the Justice League. Rather than do it himself, he decides to enlist... YOU. This being has been recently intrigued with the mortal phenomena of role-playing games and gives you the power of a 20th level D&D character of your choice (pick your edition, whichever you like). You can also select, to aid you in this challenging mission: one artifact, and four other non-artifact magic items. Plus: four scrolls and four potions (non-artifact, of course). You can be multi-classed or single class, whatever your like. Your race must be standard from a "Player's Handbook".

And, just to motivate you, the being has also captured several of your family and friends and placed them in a far-off dimension, sealed away from scrying and the like. His minions will kill them if you don't "play along". If you give it the old college try, and fail, he'll let them go. If you win, of course, he'll let them go. He'll know if you're faking via periodic check ins (remote viewing and mind reading, very subtle, as to not interfere with your plans).

Bonus: if you win, you're allowed to keep your powers, and move yourself and loved ones to a dimension of your choice, or you can decide it was "all just a dream".

So, the choice: What class(es) do you choose? What artifact and magic items? And how do you kill the Justice League?

Or do you take the chance and try to face the neigh-omnipotent being, knowing that your family will almost surely die? The Justice League can do almost anything, but do you take that chance (after all, they are already captured and this being, let's call him the "Dark Game God" really doesn't want his fun to be spoiled...)

The targets (current comic DC power levels):

Superman
Wonder Woman
Batman
Flash (Barry Allen)
Aquaman
Martian Manhunter
Green Lantern (Hal Jordan)

... good luck...!

[Beadle]

I must think on this.

But I love the idea of a “neigh omnipotent being” instead of a nigh-omnipotent one.

Just this all-powerful horse-god.

[Shai-Hulud]

20th-level Wizard.

I'll choose the other stuff, artifacts and whatnot, after I get empowered. Since as a 20th-level Wizard I'll have much greater knowledge of all that.

No coersion is necessary. I'm bored with the Justice League and am happy to bump them off. Honestly, I would have done it for free. My nigh-omnipotent sponsor needs to work on his nigh-omniscience, apparently.