Mortal Kombat 11 has a ton to unlock.
From new characters to a seemingly infinite collection of weapons and skins, finding everything is a tall order.
The most significant unlockables (including the only unlockable character) can be found in Story mode, so if you are looking to start your unlocking spree, thats your first destination.
Source: N4G PC Mortal Kombat 11: How to unlock everything