When removing my diff plug, probably the first time since 1988, I got it off only after using a 3 foot pipe around the ratchet. I wasn't able to budge it (even with the pipe) until I got up from on my back under the car, and on my knees, behind the car, and then pulled on the pipe.
2003 S500 Black/Charcoal
1990 560SEL 61k Arctic White/Grey
1988 420SEL Black/Palomino Sold @ 85k
1987 420SEL Midnight Blue/Grey
1986 420SEL Diamond Blue/Grey
1983 380SEL Champagne/Palomino