klefki has high enough attack to do actual damage with play roughFoul Play is better though on that set, hell you could even use that set without an attacking move to make room for Spikes.
4 Atk Klefki Play Rough vs. 252 HP / 0 Def Heracross: 206-246 (56.5 - 67.5%) -- guaranteed 2HKO
4 Atk Klefki Play Rough vs. 0 HP / 0 Def Mienshao: 246-290 (90.7 - 107%) -- 43.8% chance to OHKO
4 Atk Klefki Play Rough vs. 252 HP / 0 Def Umbreon: 152-180 (38.5 - 45.6%) -- guaranteed 3HKO after Leftovers recovery
4 Atk Klefki Play Rough vs. 252 HP / 4 Def Sableye: 204-242 (67.1 - 79.6%) -- guaranteed 2HKO after Leftovers recovery
4 Atk Klefki Play Rough vs. 0 HP / 0 Def Mega Absol: 246-290 (90.7 - 107%) -- 43.8% chance to OHKO
4 Atk Klefki Play Rough vs. 0 HP / 0 Def Flygon: 194-230 (64.4 - 76.4%) -- guaranteed 2HKO
4 Atk Klefki Play Rough vs. 0 HP / 0 Def Scrafty: 288-340 (106.2 - 125.4%) -- guaranteed OHKO
4 Atk Klefki Play Rough vs. 52 HP / 0 Def Kyurem: 176-210 (43.5 - 51.9%) -- guaranteed 3HKO after Leftovers recovery
4 Atk Klefki Play Rough vs. 252 HP / 0 Def Mega Ampharos: 156-186 (40.6 - 48.4%) -- guaranteed 3HKO
even against stuff that isn't weak to fairy
4 Atk Klefki Play Rough vs. 0 HP / 0 Def Starmie: 93-111 (35.6 - 42.5%) -- guaranteed 3HKO
4 Atk Klefki Play Rough vs. 0 HP / 0 Def Azelf: 109-129 (37.4 - 44.3%) -- guaranteed 3HKO
4 Atk Klefki Play Rough vs. 4 HP / 0 Def Porygon-Z: 109-129 (34.9 - 41.3%) -- guaranteed 3HKO
4 Atk Klefki Play Rough vs. 4 HP / 0 Def Gardevoir: 115-136 (41.3 - 48.9%) -- guaranteed 3HKO
granted the ones that aren't weak to fairy are all frail stuff but foul play can be unreliable and no attacking moves makes you taunt bait