A tall Alcaraz would be unbeatable. Djoker himself said how incredibly well Alcaraz served in the 2024 Wimbledon final. He hit serves up to 136 mph.
A 6 foot 4 Alcaraz would be unbeatable.
The thread is asked for the most unbeatable hypothetical player, not the most overrated.
The most overrated would be a hypothetical 6 foot 7 Andy Murray. A very tall Andy Murray would not win 600 consecutive matches. Now granted, he’d win 5-6 CYGSs, since after all, even the real version of Murray is the goat. But this nonense about 6-7 consecutive 90-0 seasons is going way too far.