The move Pursuit has a priority of +7 when the opponent tries to switch out.
+6 Switching out, rotating, using items, escaping
+5 Helping Hand
+4 Magic Coat, Snatch
+3 Detect, Endure, Follow Me, Protect, Fake Out, Quick Guard, Rage Powder, Wide Guard
+2 Feint, ExtremeSpeed
+1 Aqua Jet, Bide, Bullet Punch, ExtremeSpeed, Fake Out*, Ice Shard, Mach Punch, Quick Attack, Shadow Sneak, Sucker Punch, Vacuum Wave, Ally Switch
0 All other moves
-1 Vital Throw
-3 Focus Punch
-4 Avalanche, Revenge*
-5 Counter, Mirror Coat
-6 Roar, Whirlwind, Dragon Tail, Circle Throw
-7 Trick Room, Wonder Room, Magic Room, fleeing
The number refers to the move's priority.