Mortal Kombat 1 gives player 1 an unfair advantage
Developers are looking into the issue and will hopefully have it resolved soon.
It's a big day for all the younger siblings of the world as Mortal Kombat 1 has a genuine issue if you pick player 2. If you end up in the player 2 slot, your combos won't be able to fully connect. A strange issue, but one that has been shown in YouTube clips and picked up by prolific players.
Regardless of which fighter you pick, which Kameo you have, or your stance, you'll not be able to connect combos in the way that player 1 can. While the WB Games bug portal does not list a reason behind this issue, players believe it's a problem with the hurtbox for player 1.
Fortunately, the bug portal does say that the problem is under investigation, meaning we should have a fix sooner rather than later. Until then, there's a good reason for you to avoid picking player 2 if you have a friend over for a game of Mortal Kombat 1.