get Explosion Damage From Entity
Mirrors the vanilla blast-power setup of explosive entities.
TNT minecarts use the current speed to reproduce vanilla's upper-bound radius because net.minecraft.world.entity.vehicle.minecart.MinecartTNT#explode multiplies the speed term by server-side randomness.
See also
EndCrystal. hurtServer
Primed Tnt
Minecart TNT. explode
Creeper