Mod Corrupted

I downloaded the plugin that lets you add end biomes, and its requirement. It crashed. I deleted it, all the stuff I made with it, and turned off plugins. It's still crashing. I loaded up another mod, it's completely fine, just the one I added the plugin to stops working entirely. If I can, how do I fix it? I've tried regenerating the code, regenerating code and build. Nothing works. I've spent a while making it, and to have it end now would be really disappointing because I installed a plugin that crashed it.