Now that Merc is awsome. What kind of engine does it have?
I dunno about that one, but a review of the Brabus-tuned 'Black Edition' Unimoog (Stock engine

👎) had around 400HP, and 1100Nm of torque. Gear-ratios prevented it from crossing 80KM/h, and it was estimated to reach 120KM/h max, with a proper road-geared differential. 12 Tonnes, 400HP, and more torque than the Veyron. The review stated, that car just doesn't stop off the road... But I guess they weren't crawling, but more of a light-mudding and regular off-road driving.
Yet, the ultimate winner, IMO, in stock off-roaders will always be the Tatra ATC trucks. Those 6x6s were originally built for the Czech army, but they also compete in the Dakar, and on a thourough off-road test done in a local magazine, the car passed a climb that no regular off-roader would've passed, and most of the modded SUVs would've had troubles with, at full-speed.
(Yes, they also make 4x4 and 8x8 versions)