- First he has a Level 88 Pikachu. It has the Light ball which will double its Attack and Sp. Atk. stats. It is also pretty fast unless you train around its level. The only weakness is Ground type so I recommend Earthquake from the Victory Road.
The Pokemon will be sended out depending on the Pokemon on your side that is out.
I'll say he sends out an Snorlax. It has ton of HP and it has Blizzard so keep Grass and Flying types away from it. Use a strong fighting type attack has Close Combat or Aura Sphere.
The next on my list is Lapras. This Pokemon also has a TON of HP!! The best hits are Electric type attacks so use something like Thunderbolt or Thunder. If you use Meganium, it might get hit with Blizzard although super-effective. Fighting is good too. Rock is also good except the disadvantage of Blizzard.
Next is probably Venasaur. It has a weakness of Fire, Flying, Pyschic, and Ice. The red Gyrados or a regular Gyrados's Ice Fang is useful here or give it Flamthrower.
Blatiose is up. I has a weakness of Electric and Grass. The Grass type has the weakness again- Blizzard!
Finally is Charizard. It has a 4x weakness to Rock type. Electric is good too. The Ice type is regular damage to Charizard due to fire type. Ground dosen't effect it due to Flying type.
Note- Hail is falling all the time so that means Blizzard is 100% accuarcy.
A good Strategy for stopping Pikachu from Volt Tackle is paralyzing it. That means it will cut its spped by 75% percent!
Red doesn't use berries so thats out of the list.
Don't use Ho-oh or Lugia or any Kanto bird because of the Flying Type or Pikachu.
Make sure you buy lots of healing items, X items, and anything else you will need for the fight. You will need HM Pokemon for the climb to the top of Mount Silver so use like 3 Pokemon for fighting.