Depending on levels -
Venusuar
Charizard
War-- whatever Squrtles final evolution is
Mewtwo
Wigglytuff
Clefairys final evolution
Hypno
Next time, try to NOT delete other's answers, if you don't have a better one yourself. Here's what you should NOT delete:
(Pokemon within parentheses, (), are Pokemon who you must link with another game to get, but still works in firered and leafgreen)
Strongest Pokemon according to me based on allround stats includes:
Mewtwo
(Mew)
Any of the three starter pokemons final form: Charizard, Venusaur, Blastoise
Tyranitar
Dragonite
(Lugia)
(Ho-oh)
Gyarados
Moltres
Zapdos
Strong Pokemon in other fields (with following strenghts and weaknesses):
Chansey: (Good: lots of HP, self-generating moves. Bad: very low atk and defense)
Snorlax: (Good: much HP, pretty strong atk and spec. defense, self-generating moves. Bad: very low speed)
Steelix: (Good: defence, Bad: atk, sp.atk, sp.def, speed)
(Shuckle): (Good: Defence and Spec. Defence. Bad: everything else)
...And so on.
Please feel free to make this list longer, so that everyone who reads this answer can get some advice from it.
Your Rival
You can only catch them in Pokemon fire red.
Trade it from leafgreen or fire red
Only in LeafGreen not in FireRed. Sorry.
you cant you can only get it in fire red sorry go and get fire red if you want arbok
there are 151 between leafgreen and fire red
you cant
YES
you don't you get it in fire red
You have to trade it from Fire Red
bellsprout and what they evolve into
The same Pokemon in fire red, except for a couple.
You can't. have to trade from fire red
Your Rival
Pokemon fire red is better.
You can only catch them in Pokemon fire red.
You have to trade with someone who has fire red.