Raiden's been one of my favorite characters since the early 'Mortal Kombat' days, so unlocking him in MK1 had me hyped. The process isn't too complicated, but it does require some grinding. First, you'll need to play through the Classic Tower mode on at least medium difficulty. Raiden unlocks after you beat the tower with any character—no secret inputs or hidden fights needed. I remember sweating through a few matches against Shao Kahn before finally seeing Raiden light up on the selection screen.
If you're like me and prefer story-driven unlocks, MK1's Krypt used to have him hidden behind a specific tombstone interaction (though newer patches might've changed this). Back in the day, I spent hours punching walls for coins just to open those chests. Nowadays, I'd recommend checking if he’s part of seasonal rewards or premium unlocks if the classic method doesn’t work. Either way, getting to spam his lightning attacks never gets old.