i have tried it with ultra balls, timer balls, net balls, nest balls, heal balls, repeat balls, & dusk balls but i cant catch him?
Suicune is hard to catch just bring a lot of Ultra Balls and use a status move (Thunder Wave, Sleep Powder, etc) on it.
Hope This Helped :D
You just have to keep trying. Legendaries aren't easy to catch. One way to prevent Suicune from running away is by getting a Crobat to use Mean Look on it, so it can't escape. And the same Crobat can put it to sleep by using Hypnosis, making it easier to catch. Another way you can prevent it from running away is by having a Pokemon with Arena Trap/Shadow Tag in your Team(Aka Dugtrio and Wobbuffet).