This works on every character except Squiggly and Painwheel. It should be noted that the timing on Double is slightly faster paced on the jHP, and the timing on Val needs to be slightly longer on the jHP. Val is slightly finicky in general so you have to be precise on her. For Painwheel, you can just add a sMKx1 after the cLK and the assist kill should work fine. Squiggly needs a minor variation I tried below.
There are 2 notes about how to do this assist kill:
1. Delay the jump cancel jHP after the launcher. You have to do it so that you cross over the point character with a rising jHP that still faces the direction of the assist. It sounds a bit unintuitive, but once you see the timing for it you can nail it down regularly.
2. Picking up the assist when behind you. When you cross over with a jHP and land with a cLK, the assist can be either in front or behind you. If in front, then you can just repeat, but if behind you, you have to react with just doing cLK cHP and wait for the assist on the way down and catch again with another Light button. Once you know there are 2 situations to look for, you can react to either one easily.
This is the same assist kill but on double since idk I was bored and thought maybe people would want to see the faster timing.
This is a Squiggly Assist kill.
The thing to note about it is that when you cross over, you don't have to delay after the launcher for the jHP like in the other ones, you can immediately jump cancel and still hit with jHP from behind.