We went through this too, I got him some new exciting bath toys that light up, some drops that make the water colour change and really made it a big deal him picking which colour to make it, and having him help me run the bath and get everything ready. It has massively helped!
Same here, he screams and absolutely refuses to go in. Last time I went into the shower with him, because in the bath, he won't sit down and I couldn't even wash his hair. In the shower, omg....the scream was as if I was pouring down the boiling water. I don't know what happened....(((
When my son did this, I stopped the bath and just washed with a flannel. After a couple weeks he was happy to go in again.
We ended up having to have one of us get in the bath for a while with her and we went all out with bubbles, bath bombs, bath lights that kind of stuff