I think it’s pretty obviously always going to be the NFL player just given the disparity between a top team in the nba and a lower seed. That’s not the case in football in most instances. The games are almost always competitive. 
As far as absolute juggernauts go, the KD Warriors for certain.  But the path to the championship game was much tougher for Brady and once he got there, every game was decided by a couple points.  Outside of the years that he had to go through the Celtics and Pistons, LeBron never had superior competition out East.  The whole “do it in the west” thing meant take those same Cavs teams and Heat teams and run through the west like that - not that he could do it but not as easily.  
Brady on the other hand had to play the Raiders, Steelers and Rams during his first SB run. Then there Titans, Donovan Eagles, Steve Smith Panthers , Peyton Colts, the Ravens, LT Chargers, Mahomes Chiefs, high powered Falcons, Seahawks and so on. It’s not really all that close. Bron has the harder series but overall? Match up to match up? It’s easily Brady.