Speed, or SPD, is the stat that determines which Nanovor moves first in a battle.
Hexites are known for having the highest SPD stats of any Nanovor, closely followed by Velocitrons, with Magnamods being the slowest. SPD works like this, as quoted from Wikipedia:
The nanovor that goes first in a battle is determined based on every nanovor in the battle's speed. It works like a raffle. For example, in a battle between a 50 speed nanovor and a 20 speed nanovor, the first will have 50/70 chances of going first, and the second 20/70 chances of going first.
Hexites, such as Spike Spine, are very fast. Employ Hexites to finish off enemies with low health without a scratch!