So I was surfing on the internet and discovered that Sheik can chain grab with her down throw and up air. It had me thinking if Luigi could do something like this since I'm a Luigi main and that he not be so bad in the latest Smash game. I was basically desperate to find ways to make Luigi's potential far better. I found something incredible - thanks to his new down throw, the new placement of his down air spike hitbox and his better grab, Luigi can chain grab all characters (except Bowser) with his down throw and down air.Luigi's new down throw has far lower knockback than before, making it possibly one of the best combo starters in the game. Luigi's down air is now easier to land the spike hitbox. The hitbox is now located closer to his ankles rather than his hips. If you follow up a down throw with a down air spike at low percentages, the opponent will fall straight down but not slam to the ground until around 70% depending on its weight. You can tell that you spike beforehand by looking for longer than usual hitstun (caused by the spike hitbox). It's at this moment that you IMMEDIATELY fast-fall and re-grab as soon as you land on the ground.To summarize things, here's how it works:1. Down throw.2. Short hop.3. Down air spike.4. Fast-fall immediately and re-grab.Here's a couple of GIFs of the chain-grab. Note: All the opponents below start at 0%.Luigi can fully perform this chain grab on most characters to 65-75%. Some characters require you to wait a little bit before you jump to spike, such as Pit, Dark Pit, Villager and Sonic. The hardest characters to perform it on (aka characters that can only be grabbed once or twice) are Mario, Luigi, Peach, Dr. Mario, Kirby and Jigglypuff, although you can still use the second grab to start off a normal combo. The rest of the roster can be grabbed about three to four times, such as Rosalina. R.O.B. can be fully chain grabbed, but the fifth and final spike requires you to do a full hop. Bowser is the only character who cannot be chain grabbed.The same method with a full hop allows Luigi to use this as a finisher near the ledge, as show below. Obviously, this can work on all characters. Note: These opponents start at around 100% or above.Experiment on each character about what percentages you can perform this on, how long, and when to spike each time (early or late?). The best way to practice this is in Training Mode.I hope you've enjoyed reading my findings. Please leave a comment if you have one.