As karthus, Your level 2 is much stronger than the enemies. Try to get level 2 first (the first wave followed by 1 melee minion) and then look for an all in. Make sure you hit 2 first to win the exchange.

The enemy will be using their abilities on the minion wave to push. Try to stand outside of the minion wave but close to it so they have to choose between pushing and poking.

Keep an eye on your mana at all times, especially at the level 2 and level 3 all in. If you run out of mana, you have no way of trading back with the enemy and you will be quite vulnerable.

The enemies all in potential is incredibly strong, try to remain as healthy as possible and back off if you’re low. If the enemy gets the chance- they will look for the all in and if you fall behind, you’re going to find it difficult to come back. As karthus, Your level 2 is much stronger than the enemies. Try to get level 2 first (the first wave followed by 1 melee minion) then look for a whole in it. Make sure to hit 2 first to win the exchange. The enemy will use their capabilities on the minion wave to push. Try to stand outside the minion wave but close to it so they have to choose between pushing and poking. Keep an eye on your mana at all times, especially at level 2 and level 3 all in it. If you miss mana, you have no way to come back with the enemy and you will be very vulnerable. All enemies in potential is incredibly strong, try to stay as healthy as possible and retreat if you are low. If the enemy gets luck - they will look for everything in it and if you fall behind, you will find it hard to return.