User blog comment:Plasmaster/Smash Study Hall: Little Mac/@comment-26196280-20151019221545/@comment-6684591-20151019232338

Also, it can be a bit hard to say straight up front what character is a good counterpick against another, for a number of reasons. This Smash iteration is very balanced, so really you could beat any character with any character if you know how to play that character effectively. Also, with no set tiers, there aren't any set statistics that say which match-ups are dominant in a match. However, I will try to give you some ideas as to what fighters would fit in those categories.

Little Mac wouldn't do very well against Meta-Knight, Kirby, Jigglypuff, Pit, Dark Pit, R.O.B., King DeDeDe and Shulk with Jump Monado Art due to their high aerial mobility and prowess in aerial situations.