Probably an ultra ball
or u cood use a timer ball after he is put to sleep. You could also try a luxury ball if u want, i almost caught him in one, im still trying to catch him.better yet use a master ball. it only takes one.
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try master ball it is the best olviously
Just be paitent and catch it with a pokeball!
MasterBall
Any pokeball will work but an ultra ball is probably best.
A Master Ball