A world overrun by the dead

Your rules provide for a number of ways to create a revenant that will effectively never rest. More of them will be created all the time. An ever-increasing tide of revenants slowly but inexorably chokes the life out of Mankind. You should probably close these loopholes.

Loophole: a revenant can't kill a dead person

If I am parsing your rules correctly, if even a single person on a particular revenant's hit list dies, but not by the revenant's hand personally, that revenant will never go away. It will simply keep on killing ... forever?

You might be able to convince the revenant 'no, really, they're dead'. Or you might not. Many people have died whose bodies were never found, especially if they happened to die in a secluded area.

Loophole: Two revenants want to kill each other

Perspective being malleable as it is, it's easy to imagine scenarios where two people hate each other, each believing the other one screwed them, and they can die close enough to each other to become revenants.

Loophole: The revenant hates everybody

This could happen in numerous ways. Take a notorious psychopathic killer who doesn't give a crap about anyone but himself. Literally, that's what a criminal psychopath is: no conscience whatsoever, an inflated view of self-worth, a huge hypocrite, cares only about themselves. So when you execute one of them, they might well feel like the entire world has done them an injustice.

Or someone who is upset and disturbed enough to go on a mass shooting could become a revenant. They felt wronged by the world enough to lash out in life, after all.

Loophole: Revenants with vendettas against entire groups

Terrorist revenants, revenants soldier revenantssoldiers killed in battle become revenants obsessed with killing 'the enemy', particularly virulently anti-semitic or white supremacist race-war true believers who die of natural causes, there are lots of ways this can happen.