/effect @p minecraft:resistance 1000000 255 true isn't so powerfull.

Even when invincible with a resistance effect with a level of 255, i managed to die, not because of /kill, not because of the void, but because of fall damage. Yea...

What i did was :

1. I put on myself a level 255 of resistance for 1000000 seconds.
2. I verified that it was working (*:* duration in inventory + no fall damage in usual ways)
3. I pulled up a trident with Riptde III
4. I tried to die landing on solid surface using the boost of the trident while in water (because thats how Riptide works).
5. I died cause of fall damage.