When Little Mac uses Slip Counter, he will move his body backwards and cover his face with his hands in a defensive pose. The move will do nothing if Little Mac is not attacked, but if an opponent attacks him, Little Mac acts like he was hit before retaliating with a punch to catch the opponent off guard, while a representation of a heartbeat appears above him. Little Mac is invincible during the attacking frames when the move is used on the ground, but not when used in the air.
During the counterattack, Little Mac takes a big step forward both if on the ground or in the air, which can be life-saving due to Little Mac's sub-par recoveries; countering an opponent's attempted gimp is therefore a risky yet beneficial tactic to extend Little Mac's recovery potential. However, this can be detrimental if the opponent attacks him in the opposite direction away from the stage, as Little Mac will rocket even further away from the stage, unable to recover.
If Slip Counter successfully counters an attack, it reflects 1.3x the damage of the countered move to the attacker, with a minimum of 10%. Slip Counter is tied for the fastest counter in the game (with Double Team and Witch Time), beginning at frame 5, but it is slightly weaker in terms of knockback compared to other counters that also reflect damage, not OHKOing until it counters an attack that deals 38.5% or more damage, causing the counterattack to deal the 50% damage cap.
Unlike Little Mac's other special moves, Slip Counter doesn't have a unique 8-bit sound if he is using a Wireframe alternate costume; in fact, the move makes even less noise since it removes Little Mac's voice line during the counterattack.
Giga Mac's version of Slip Counter also uses a 1.3x damage multiplier, and it deals a minimum of 30% damage. However, the damage cap is still 50%, and the counterattack's knockback is exactly the same as that of Little Mac's Slip Counter.
In Ultimate, there is a glitch with Little Mac's counter which occurs when attempting to counter a move with a 0x hitlag multiplier. When doing so, the counterattack will inherit the 0x hitlag multiplier for the opponent, but not for Little Mac. The opponent's Hitstun animation will also be frozen, and they can cancel hitstun with any action much earlier than usual, with a similar effect to momentum canceling from Brawl. Notably, Terry's Buster Wolf will trigger the glitch, and he can perform a full momentum cancel by quickly activating Power Dunk when launched. However, should the attacker get the reeling animation, they will be unable to cancel the hitstun early.
Special Move customization was added in Super Smash Bros. 4. These are the variations:
Countering opponents is one of the most important aspects of not only the Punch-Out!! games, but boxing in general. Little Mac's strategy to defeat most of his foes throughout the games was by dodging their attacks, or by feinting his own attack, and then following up with a series of punches while they are off guard. Countering an opponent's punch before they throw it will earn Mac a star to use for his Star Punch attack or gives Mac a bigger window to unleash an attack. In the Wii installment, countering with a star punch can OHKO opponents.
Apart from Mac's use of this strategy, the use of a full crouch stance before throwing a punch is also used by Glass Joe in Title Defense mode in the Wii version of Punch-Out!!, where he delays his hook by assuming a similar stance before throwing it. The concept of countering is also used by Don Flamenco as his overall fighting technique, who will not attack until Mac throws a punch of his own, and then dodge or block before throwing a slightly over-the-top punch himself. Aran Ryan's fight has a similar concept, but in reverse; Little Mac must anticipate and counter Ryan's punches in order to deal any significant damage.