How do you make a lich a good guy?

How do you make a lich a good guy?

Call them an arch-lich

...

A) Change what it means to be a lich so it's not just evil wizards willing to sacrifice their humanity to attain immortality, thus letting good wizards become liches too.
B) Make the lich remorseful; 1000 years of loneliness tends to drive them mad, but there's always the chance a lich would swing the other way and realize "hey maybe other people are actually worth hanging out with and I should be less of a dick to them." He probably won't be great at doing good, but he's trying!

If you can't figure out how to do it yourself, I have zero faith in your ability to do it well.

make the PC's the bad guys

They usually do that on their own.

Depends on the setting. Liches are almost always evil due to inherent nature of necromancy, though most times it usually leaves the lich with their own free will. Have it be the spirit of a sorecerous hero who was raised to fight off greater evils.

This is actually an idea I've been looking at for awhile for a BBEG. Ancient king raised from the dead to fight an immortal dragon he defeated during his reign, but because abhorrence of necromancy he's effectively being hunted down.

First, make him not a murderhobo. Then, make him speak inspirational speeches, make good political decisions,

Allows mortals to live in his necrokingdom, trades, does diplomacy. All for the sake of strenghtening the kingdom and keeping citizens satisfied and working well. Free thought, free will, maybe even democracy and capitalism. Sounds kind of dindu, yea?

All for the sake of his mad dream of ruling the galaxy someday. Scientists and workers will make something to reach for the sky, and... THE STARS WILL BE CONQUERED, AND GODS WILL KNEEL OR DIE. ALL WHO OPPOSES THE WILL OF MASTER OF DEATH AND LIFE SHALL be persuaded to not oppose or PERISH.

By doing it? Negative energy isn't evil in of itself and if its your setting you can just do it because your the creator or dm.