.375 H&H Sako AV left hand using Winchester 300 grain soft points, 5 rounds from an offhand standing position. The recoil was mostly a very generous thrust to the upper body.
2 nd to that was a Weatherby MK V left hand in .340 Weatherby using Speer 275 grain soft points hand loaded to almost 2900 f.p.s., 45 rounds from the bench, no lead sled back then (1984), no porting. A most brutal session.
Have not experienced this personally but have been told that of all the commercially made dangerous game cartridges made today, the .378 Weatherby Magnum is by far the worst experience you'll ever have with recoil as the bite and bark are equal in ferocity. Documented incidents of this cartridge literally shearing scope base screws off resulting with the scope itself free recoiling separate from the rifle. Have seen this on video and have no reason to dispute it. Free recoil is undeniably vicious and likely life altering to the shooter. Getting rattled to that degree must have a price to pay with it too.
See no need nor desire to acquire such a brute as I'm not currently being bothered by any such big assed critters that can bite back or stomp you into the dirt. But as with anything in shooting, having such a dangerous game rifle and cartridge is not necessarily the same or relevant to needing one.
As in many such experiences, more often than not, less than 1 box of 20 rounds is what you see accompanying the sale of the near new shoulder busting rifle as the novelty soon gives way to the reality of an often brutal recoil. Hence the old phrase of how they "kill at both ends!"