If your rater has a personal problem with you, what would you do?

Too often ratings are handed out based on likership vs performance, potential. I had the same situation as you. My rater straight up said he didn't like me, my oer is a pure reflection of that. I am appealing it now.

I don't know about you Chief, but I my case I be talking to the SR and probably that would be the last day I work for that rater, this is also an issue you should bring to your senior warrant, they for sure could help you.

Performance, performance, and most importantly, PERFORMANCE.
That is what you should be rated on, with very little in the way of exception. If you believe that the issue has substance and may scuttle you in the eyes of your rater, my advice would be twofold:
1. Document carefully what you have done and bring it to your quarterly OER counselings, You'll know early on if your rater disagrees with your view of your performance, and what the substance of that disagreement is. This will come in handy if you have to pursue redress later.
2. Do reconnaissance. What does this former Soldier have an axe to grind about? What do others that are in the know feel about it? Why is your rater drinking the Kool-Aid? This information will allow you to organize relationships into threats and allies and will also come in handy if redress is necessary.

I can't really envision a situation short of pushing me into releaving an officer where I would tell them I would treat them like a Private. That doesn't exactly scream the Army Value of Respect.
What precipitated that comment? It might inform on what your rater's mindset is.