Special starters are all murderous. It's too bad Crustle and Rhyperior are so slow, though I suppose you could try running a Trick Room team for them to spam Rock Wrecker in. It would also incidentally screw with all the speedy sweepers that are liable to be the default, so there's that. Also, Dialga's signature move is no longer 100% terrible. And of course -ate Pokemon spamming Giga Impact/Hyper Beam is amazing stuff.
Also, Draco Meteor, Leaf Storm, Overheat, Superpower, and Psycho Boost are all way better moves now. (Except Contrary Superpower and Leaf storm, RIP Malamar and Serperior) Spam away.
V-Create is of course the stuff of nightmares. Screw Linked, this is the true V-Turn!
Metal Burst is a nifty move, able to retaliate for heavy damage on whatever switched in with not one care given for their typing (Barring Shedinja), and then switching out yourself to something better.
Thrash, Outrage, and Petal Dance are effectively no disadvantage. Outrage is the big one of note, but Petal Dance is the strongest general-access Grass move that isn't Sun dependent, so that's actually noteworthy too.
Inflicting major status is great stuff -Prankster Will O Wisp, Thunder Wave, Sleep Powder, etc, switch out, and the fact that they switch out afterward is only slightly helpful. Toxic is basically worthless though, stick to regular Poison or Burn.
Yes pls unban Mega Gengar. It'll still be good, being really fast and really hard hitting, but it won't be broken. (Other things will be broken instead)