Had a lot of em...On Sapphire I had Lv 100
Metagross(Probably strongest), Rayquaza, Raichu(traded) and Sceptile
On Fire Red Lv 100 Charizard, and in progress a Lv 100 Dragonite, I was doing a Tyranitar to that lv and I said to a mate one day "Don't take the Tyranitar"...3 guesses no prizes what happens next lol
And Lv 100 Rayquaza on Emerald.(Keeping most of them on Lv 60 here to do battle at the Frontier...Not going well when I decided to get my Latias to level 100, it's on the way haha)
So strongest overall, I would say is my Metagross, Mighty proud of it lol, as soon as Steven decided to use one against me I thought I must have it!