Seems I can't edit/delet my post after 5 minutes :/ I hope a mod can delet the previous one
My first solo run was
Terrakion @ Expert Belt/Focus Sash/Lum Berry/Rawst Berry
Ability: Justified
Nature: Adamant
EV: 4HP/252Atk/252Spe
- Close Combat
- Stone Edge/Rock Slide
- X-Scissor
- Zen Headbutt
Watch out for CC def drops when you fight Sturdy/Sash mons and bulky ones, always save before starting a battle!
In any case, don't forget to carry healing and PP restoring items, save before each battle to understand which pokemon you can OHKO and how to deal with the others, and to re-try if you miss or get critted/haxed to death.
You can also use one move to beat a specific E4 (Ghost/Dark coverage for Shauntal, Psychic for Marshall, etc.) and then replace it with a TM if needed.
And be at level 100, of course!
Then I did some others (mainly with dual-typed mons to get the "type-solo" medals quickly):
Nidoking @ Life Orb
Ability: Sheer Force
Nature: Quiet (I found it in the Hidden Grotto, I got a nature "good enough")
EV: 4HP/252SpA/252Spe
- Earth Power
- Ice Beam
- Shadow Ball
- Thunderbolt
Volcarona @ Focus Sash/Expert Belt
Ability: Flame Body
Nature: Modest
EV: 4HP/252SpA/252Spe
- Bug Buzz
- Psychic
- Shadow Ball
- Quiver Dance
Alakazam @ Focus Sash/Expert Belt/Life Orb
Ability: Synchronize
Nature: Timid
EV: 4HP/252SpA/252Spe
- Shadow Ball
- Focus Blast
- Psychic
- Substitute
Kyurem-W/Reshiram @ Expert Belt/Life Orb
Ability: Turboblaze
Nature: Modest
EV: 4HP/252SpA/252Spe
- Shadow Ball
- Dragon Pulse
- Fusion Flare
- Psychic
Togekiss @ Leftovers/Expert Belt
Ability: Seren Grace
Nature: Timid
EV: 4HP/252SpA/252Spe
- Aura Sphere
- Air Slash
- Shadow Ball
- Thunder Wave
Rotom-? @Leftovers/Expert Belt
Ability: Levitate
Nature: Calm
EV: 4HP/252SpA/252Spe
- Blizzard/Hydro Pump/etc.
- Thunderbolt
- Shadow Ball
- Charge (lol, use Hidden Power or anything else)