Correct me if I am wrong Galan, and I don't remember exactly what the Gentry itself did but it was created by the Hand I believe. ( Pretty sure that's the name) who himself signifies the end of the story or the reader after they are done. Which in my opinion is like a Cosmic Armor Superman level being.
I I don't know if that helps or if he is truly that powerful but if CAS is the story and the Hand is the end of the story or a discarded? story then that should put him in the same ballpark.
CAS/hand>6d/5d/beyonders>multiversal/Gentry>universal
I might be way off here Stoic and just because something is muktiversal doesn't mean Thanos can't beat it necessarily as Im not sure what it's actual feats are