What is the highest priority move/lowest?

Question

I am hoping to get a Pokemon who can learn a priority move. It's part of a strategy I'm forming to beat my brother.

Also,
I was watching a youtube video by Marriland and his Lombre used fake out against another Pokemon. The foe used a regular move AND HIT FIRST.

I don't understand it.

I don't remember the episode number but it was in his emerald Nuzlocke challenge.

Answer 1

The move with the highest priority is Helping Hand, with +5 priority, although Pursuit has +7 priority when the opponent switches.

The moves with the lowest is Magic Room,Trick Room, and Wonder Room; all with -7 priority

Source