Seems like a pretty rough one. Sonya gets to set the tempo of the match. It feels like Raiden spends most of his time needing to adjust and react to Sonya. Maybe it was just because Dalphanate was playing better with Raijin, but it seems like Raijin is the better variation to go with in this matchup. Easier to stay safe, and easier to avoid getting chipped to death. As was said in the video, he wasn't getting anything from teleport or Storm Cell, so if one set of tools isn't working might as well switch to the other. I really need to put in the time to better learn both TW and Raijin, this video is a good glimpse of why knowing both is key.
Also, just another comment on the matchup (and this is going to sound pretty nerdy), but in Magic The Gathering there's a pretty influential strategy article from 1999 that people still reference a lot called "Who's the Beatdown?". Basically this guy noticed that a big reason people would lose in Magic was mis-assignment of who is the beatdown deck and who is the control deck. At any one time in a game of Magic, one person is “the beatdown” – the one applying pressure, and the other is “the control” – the person trying to defend themselves. The player who mis-assigns themselves is inevitably the loser.
Obviously there's not a ton of overlap between MtG and Mortal Kombat, but I've always thought that the "who's the beatdown" framework was a pretty decent way to look at matchups, and can be re-worded slightly to "who's the rushdown?" to make it applicable to MK. In the Sonya v Raiden matchup, Sonya is pretty clearly the Rushdown.