>>50856627You can get it on a level 14/16/17 Voltorb on Route 10 in RB and FRLG. It learns sonicboon at 17 in RB and 15 in FRLG. It's just barely not a 2hko on most pokemon at that point in the game, which is not completely useless. Either way, it's Voltorb's best option against the upcoming Geodude and Graveler spam, and probably better than its tackle on everything its electric moves aren't good against for a long time. (It only gets electric moves by level up in FRLG btw, learning Spark at level 21)
Damage calculator says a level 17 voltorb with average ivs and no evs does 5 damage to itself with tackle, with a 1/16 chance of doing 6 damage. Base 30 attack is hard to work with.