Street Fighter 6

Super quick and easy to grind out. This also satisfies the "Over the Top Victory" achievement (as long as you win all 20).
This is done in the "Special Match : Extreme Battle" section of "Fighting Ground".

• Chose Down & Out.
• Any Gimmick you'd like (you can usually win before the gimmick comes into play).
• Chose your favorite character, preferably one with a long-range sweep (Crouch + HK, + with classic controls). I chose Ryu just for the standard sweep.
• Chose whatever opponent you want, just be sure to set their "CPU Level" to "1" to make them an easier target.

As soon as the match starts, Jump towards them and press HK (), then sweep (Crouch + HK, +). This should knock them down, then just keep sweeping them every time they stand up. They should almost never block, and you'll get 5 knockdowns before the timer hits 90 seconds. If they block, just sweep again (or even just throw them). Then just mash Start or to request a rematch. After 20 matches, you'll unlock this achievement.

TL:DR - Down & Out, CPU Level 1, Sweep Sweep Sweep Sweep Sweep (Sweep)

For those who prefer video guide: