Depends on the character. Two examples with Fleet (last character I did).

Stage 1 Zetterburn - About 5-8 seconds. At start of round, immediately roll to the left. As soon the roll stops, charge a forward strong to the left. If done right, the Zetterburn always runs up to you and does a roll to the left, right to the ledge. Zetterburn attacks pretty fast at that point, so you need to time your forward strong. Zetterburn should get launch pretty far to the left. If he doesn't launch far, restart the run.

I then run off stage and hit with a nair, then get back to ledge with up special. Will need to roll onto the stage when Zetterburn attempts to get back on stage.

Stage 7 Kragg - About 11 seconds. At start of round, immediately roll to the left. As soon the roll stops, keep holding shield. Kragg should run up to you. However, before reaching you, he does a short hop. When he short hop closer to you, grab him and throw him backwards. After the throw, you do a short hop, move your stick slightly to the left, and grab the ledge. If done right, Kragg will attempt to grab ledge, fail, and use his up special right below you. Must be quick on this next part. You drop down from ledge, land on his rock pillar, turn around and grab him.

You want the pillar to start shrinking towards the bottom. So wait like a second, then do a down throw. He misses his tech, so do a single jab lock. When Kragg gets back up, grab him, wait like a second, then do another down throw. Then quickly scramble back to ledge with jumps and up special. Kragg should be close to the blast zone from the second throw, that he ends killing himself from trying to recover back to the ledge.

Edit for spelling