Sadly count abyss doesnt have many feats other than turning the infinity gems against the users... The only other time anyone has done that i believe is when thanos used the power gem on the time gem of the gardener... Other than that...
Supposedly ombipotent in his own universe... Basically could mean anything like a dormammu or shuma gorath level character... Eho knows...
For what the galactus engine has done though ill give it to the GE