1. A reality warper?
2. A time master?
3. An invincible superman?
4. An eldritch abomination?

cosmic entity

1) The Ultimate Nullifier.
2) The Ultimate Nullifier.
3) The Ultimate Nullifier.
4) The Ultimate Nullifier.

You can try to not take acid, for a start...

1. Send a note to the time master that reads, "I warped your mom last night, if you know what I mean."
2. Send a note to the invincible superman that reads, "I spent a few centuries with your mom last night, if you know what I mean.";
3. Send a note to the eldritch abomination that reads, "I saved your mom from a broken helicopter teetering at the top edge of a skyscraper last night, if you know what I mean."
4. Send a note to the reality warper that reads, "I pixie dusted your mom last night, if you know what I mean."

I don't think there exists a planet with rotation that a night lasts a year by any measure, let alone 300 or more.

Simple, use a MacGuffin!

Part of me wants to respond, "He's a time master."
Part of me wants to discuss the peculiarities of Venus.

Do a barrel roll!

up-up-down-down-left-right-left-right-B-A

1. Quickly. Don't give him time to warp anything. Use deceit or trickery, don't confront him or give him time to do his thing. The faster you stab at his neck, the better.
2. Secretly. Poison his food or drink in such a way that no one notices or has a way to pin it on you, so even if he sees his own death from the future, he'll be unable to figure out who caused it. If he avoids coming to the present to prevent his own death, then you've already won.
3. Beating someone invincible is impossible, so you need a different approach. The best thing to do is send him elsewhere, preferably somewhere he'll get lost and die of old age, lack of food or whatever.
4- I actually don't have a clue what an Eldritch abomination is or what it can do.

Mystic Eyes of Death Perception

Maybe we could do a little of both. At some point in the future, perhaps we can expect one of the planets to slow to the point that it becomes tidally locked to the Sun, like the Moon is to the Earth. So he can travel to that moment and then spend centuries of night with superman's mom on the dark side of said planet.

At least two of those are answered by playing the Freedom Force games...