PorygonZ- (It has to have Adaptability to work.) Hold Silk Scarf. Use Nasty Plot once or twice then Hyper Beam. If the opponent has mediocre or lower defense, it'll almost always a one-hit kill. Except for pokemon that are Rock, Steel, or Ghost-types.
Machamp- (It has to have No Guard to work.) No Guard makes it so any move from you and your opponent WILL hit. So teach it powerful moves with low accuracy for great results. Like Dynamic Punch, it's the same type, very powerful, used on a fighting-type quadruple weakness pokemon will give more power, and as a bonus: The opponent get's confused. Give Machamp a Fist Plate for extra power!!!
Rattata or Raticate- Put one of those at a low level into battle. Have it know Endeavor and Quick Attack. Give it a Focus Sash. When a high-leveled opponent attacks it, it will most likely die. But with the Focus Sash, it is leaved with 1 HP left. Use Endeavor to make the opponent have only 1 HP as well. On the next turn, use Quick Attack for the kill. This is a one-use per battle strategy. But it is really good!
Absol- It doesn't have to be Absol, it only has to be a pokemon with Super Luck. But I highly recommend Absol to do it because of high speed and power. Give it a Scope Lens to improve the critical hit-ratio. Super luck will help it a lot more if it has that too. Teach it moves that have high critical hit-ratios. If they're physical, then they'll do more damage. This way, almost every move Absol uses will be a critical hit!
I hope these strategies helped! I'll make more combos some other time. PLEASE RATE! I worked hard to type all this!!!