Nothing beats stacking so much TNT and blowing it up for your screen to freeze for 20 seconds, only to show you one frame of everything going to hell before freezing again

Summoning thousand of entities and see much you can summon before your computer burst into flame

Eh since 1.15 tnt hasn’t been the best method of stress testing anymore.

Mass spawning entities is prolly the best way to go.

My favourite one is superpi

Use blender benchmarks, I’ve honestly used it to consider what graphics cards to buy