com.google.gson.jsonsyntaxexception:com.google.gson.stream.malformedjsonexception:unterminated string at line 1 column 48684 path $.versions[211].null

It seems you had a hard crash at some point for some reason, or maybe your internet cut out while connecting. You can fix this error by deleting multiconnect's translation cache. Delete the directory at .minecraft/config/multiconnect/caches.