Virizion's Base 192 Attack is below-average by PvE standards. Paired with an awful movepool in Quick Attack, Zen Headbutt, Close Combat, Leaf Blade, and Stone Edge, Virizion is...not good, to say the least. It lacks a STAB Fast Move, and Close Combat is an underwhelming Fighting-type Charge Move; on the Grass front, Virizion has to compete with Roserade and the Frenzy Plant starters when it doesn't have a Grass-type Fast Move. Anything that you would want to use Virizion for, Breloom does better.
The good news is, Virizion's Grass/Fighting typing means that it has a 4x weakness to Flying. While its bulk is actually very respectable, this Flying weakness means that Virizion is easily duoable with an assortment of budget Flying-types.
Minimum viable levels assume Best Friends, no Weather, no Dodging.
Italics indicate a Legacy move.
Leaf Blade is extremely easy to duo. Assuming you're using Level 30 Honchkrows, you will win with around 40 seconds left on the timer, even accounting for relobby time.
Close Combat is slightly harder than Leaf Blade, requiring slightly more powered-up counters. However, the overall difficult is still very easy; Level 30 Honchkrows will be able to win with around 20-30 seconds left on the timer, accounting for relobby time.
Stone Edge is much harder to duo, and relobbying twice is a real concern. While you should still have plenty of time even with 2 relobbies, it can be taxing on your Revive/Potion stash. If you can consistently dodge Stone Edges, you may be able to avoid a 2nd relobby, or avoid relobbying at all with Level 35+ counters, while only losing ~20 seconds compared to a No-Dodge strategy.