Maximum difficulty, found a lvl 95 and decided to tame it... I started with 48 tranq arrows and ended up with 1 left. It is extremely easy to tame for lower levels and is a great mobile narcotic factory.
If you wanted to tame a level 300 bronto with only your fist and mejoberries you would need to punch it 11785 times and feed it 1334 mejoberries over the course of 8 hours and 15 seconds. This could in theory work quite nicely if the bronto got stuck from some rocks, until you realize the amount of recoil damage from punching. But this isn’t over yet, if we were to create a small stone structure with a bed inside we could respawn infinitely allowing us to punch the bronto with our many lives. We would also put some spare beds in the structure just in case one breaks or stops working. Now I have wasted your time and mine by typing this. But at least you know.