Jirachi is definitely not one of the strongest pokemon around, but at least he has wish powers. A lot of good that will do him. Ness will beat him with his PK powers. Ness has fire and green energy attacks. Ness wins.

Update! I think that Jirachi’s array of powerful pokemon attacks will get the job done in this round. Nothing can stop a well planned Hyper beam and his speed isn’t that bad either. Jirachi wins.