I lost my whole Lvl 60+ Team: The frustrations of being a pokémon master

[Maxpphire]

Actually the Pokemon Missingno didn't do much to damage the game.

If you battled with it in your party, the sprites will be scrambled, but is fixed when you viewed the stats of a non-glitch Pokemon, it caused your Hall of fame to be all funky if you viewed its stats, then is made a 128 of the 6th item in your bag.

Thats all.

Other Glitch Pokemon existed back then and may have ruined some parts of your game but Missingno was legitimately the "safest" of them all.