Counterattack

You reduce the number of attacks a creature can take by 1 until the start of your next turn. This includes any attacks granted by the Attack action, Extra Attack, or Action Surge. The triggering Attack action by the creature is expended even if their number of attacks is reduced to 0. Example: you use this spell with a 6th level spell slot on a fighter level 11 as he starts an Attack action. The fighter's number of attacks are reduced by 4. So he loses his Attack action with its 3 attacks, and when he takes Action Surge, he loses 1 attack from his second Attack action, being able to actually attack only twice instead of 6 times.

At Higher Levels. When you cast this spell using a spell slot of 4th level or higher, the number of attacks reduced is equal to the level of the spell slot you used minus 2.