I got a level 110 and a level 90 pretty easily on aberration without much hassle. I think I did it on a ravager and the megalosaurus was unable to pull me off then just tranq them, it shouldn't take too many tranq arrows and I was using a crossbow
These bad boys/girls only spawn in the artifact of the cleaver cave on mobile. They’re relentless during the night time so only knockout during day time. Oviraptor eggs will be the most time consuming part of trying to tame a mega.