I like the Attitude Adjustment (not the name, the move itself). However, there are big differences between the Attitude Adjustment and the Last Ride, and the 3 listed give the Last Ride the nod as the higher-impact move.
1. Force: With the Attitude Adjustment, Cena flips the guy in mid-air, and lets his opponent fall to the ground. With the Last Ride, Undertaker gets a lot more height and slams the opponent down with force, creating a lot more impact.
2. Height: Another difference would be the height. With the Attitude Adjustment, Cena (who is 6'1" according to WWE), so when he takes his opponent up, they get around 7 feet up, and their head never gets above that. With the Last Ride, the Undertaker (who is 6'10.5" according to WWE) lifts his opponent over his head for a powerbomb, then hoists the opponent up as high as possible (by the opponents attire). Doing this gets the opponent up around 9 feet, but the the opponent is vertical, which means his head is around 12 feet up, and with the velocity Taker puts into the slam to the ground, the guy hits the ground harder from a higher point.
3. Head Damage: Finally, the third difference between the Attitude Adjustment and the Last Ride is the potential for a whiplash effect. On the Last Ride, the head is coming down with force from somewhere around 12 feet, with the head coming down unprotected. With the Attitude Adjustment, the head comes down from 7 feet, and, since the opponent is being flipped in mid-air (and his head is protected from landing first by Cena), there is very minimal-no impact on the head.
So basically, the Last Ride is a higher impact move, but the Attitude Adjustment is still a high impact, quality move. The main advantage to the Attitude Adjustment is that Cena can do the move to anybody, while the Undertaker will have a harder time doing it to Super heavyweights (I think taker did it to Mark Henry once, but I don't think he got the elevation, and he picked him up out of the corner).