ACID Property:
A - Atomicity : Either full or none. Do or Die.
C - Consistency : After transaction, Database is unchanged.
I - Isolation: Concurrent transaction without making Database inconsistent.
D- Durability: When a transaction is over, all changes made are permanent.
So,
1.read(x)
2.x=x-50
3.write(x)
4.read(y)
5.y=y+50
6.write(y)
If the above transaction fails at 3rd step (i.e.) write(x) , the transaction is not taking place completely.
According to Atomicity definition above do or die, It can't do. so DIE.
There can be some chances for all other properties but the onw which get affected directly is ATOMICITY Property!