Always furious and tenacious to boot. It will not abandon chasing its quarry until it is caught.
It stops being angry only when nobody else is around. To view this moment is very difficult.
If approached while asleep, it may awaken and angrily give chase in a groggy state of semi-sleep.
It becomes wildly furious if it even senses someone looking at it. It chases anyone that meets its glare.
It will beat up anyone who makes it mad, even if it has to chase them until the end of the world.
— Pokédex entries (via PokeAPI)