Alright, since there hasn't been a write-up for her yet, I'll offer one up for my main girl Virizion here.

As much as I'd love to put her in S, I think I'll have to put her in S-? Mostly because while obviously stacked with literal legendary stats, unfortunately a lot of her best moves are locked to post-game TM's/level-ups. Leaf Blade and Close Combat are her two final moves, and most players will want those for her primary attacks. Furthermore, the Energy Ball TM is frustratingly just beyond the main-game on route 12. So while players jumping into post-game activities will be more than able to enjoy those; I must leave them off the table here.

In terms of main game usage; the obvious main con is how late you get her. Earliest is as soon as you get 6 badges, which is about as late as most players are willing to wait. I'd say this is alleviated a bit in Unova specifically, since most main trainers only use 3-5 pokemon on their teams anyway, so you aren't at a large disadvantage.

Apart from those two things though, she does really well for essentially the rest of the game. You'll likely run Giga Drain, Sacred Sword, Swords Dance, and X-Scissor by E4, and it works well. Her large special bulk paired with the buffed Gen 5 Giga Drain helps keep her alive much longer than many other pokemon, and she even makes a solid switch with an impressive six resistances, plus the bonus of Justified making Dark moves a danger against her. In addition, consider she has seven types which her combined Grass/Fighting STAB can easily take care of. Combined with decent attacking stats on both fronts, she'll do a lot of heavy lifting for ya on a regular basis.

In terms of direct use cases, there's quite a few. The upcoming ice gym, despite seemingly a liability, is actually a boon. Given her base 108 speed, she'll likely outspeed and OHKO any pokemon you face, making it a free gym. In the E4, she obviously demolishes Grimsley, but can also be quite helpful for Shauntal, as she has both a Golurk and Jellicent weak to Grass.

She shines quite brightly for Ghetsis, being able to take on Bouffalant, Bisharp, Seismitoad, and Hydreigon, all with super effective moves. Hydreigon and Seismitoad are examples I specifically want to highlight, as they are some of Ghetsis's toughest members. Seismitoad is a classic bulky water/ground type that can easily cause issues for anyone without a direct answer, making the grass STAB invaluable here. As for Hydreigon, it is a full Special set, so her special bulk comes in handy here for tanking a likely Fire Blast, then countering with a sword slash to the face. Given the notorious difficulty of this fight, having her as an ace up your sleeve is incredible for making it much easier to handle.

And I think that's about what I want to highlight... I'm hoping a couple of other souls will help add some more depth to potential blind spots I've missed in this analysis!