I don't normally call people out, but fuck it. I'm going to because I'm a bit annoyed with the ignorance and lack of knowledge of a
real battle situation shown:
Yeah but...
252 Atk Choice Band Victini Bolt Strike vs. 252 HP / 252+ Def Slowbro: 238-282 (60.4 - 71.5%) -- guaranteed 2HKO after Leftovers recovery
252 Atk Choice Band Victini Bolt Strike vs. 252 HP / 252+ Def Suicune: 232-274 (57.4 - 67.8%) -- guaranteed 2HKO after Leftovers recovery
252 Atk Choice Band Victini V-create vs. 252 HP / 0 Def Mega Ampharos: 176-207 (45.8 - 53.9%) -- 47.7% chance to 2HKO (still faster at -1)
Assuming Ampharos is already evolved, its a goner if it isn't.
Pursuit is the only solid way to deal with victini and its pretty flimsy from what I can see. -1 Victini is still considerably bulkier than most offensive threats in the metagame right now. (puts him at 61, above mienshao, houndoom, honchcrow, darmanitan) Especially when you consider victini's very solid base 100 HP.
But every example you've given requires a sacrifice. And if you're prediction is off with the pursuit, Victini can likely end up taking the pursuit user out as well. Even banded heracross can't take victini out at -1 unless it switches out. So it's really a game of chance.
Considering Hydreigon which absolutely can be dealt with very easily was "Potentially broken" I'm just curious why victini was never considered for this as its counters are all very flimsily and it its not afraid of un-boosted pursuits even at -1.
Ok, there's a lot of things I find wrong with this, so I'll break it down. Yes, Victini can use Bolt Strike to predict a Slowbro / Suicune switch-in. While this will aid in breaking Suicune, Slowbro has Leftovers and Regenerator. This means it will heal off ~39% of the damage instantly just by switching out after Tini hits it. So, in essence, you're doing 21.4%-32.5% damage. Not a whole lot and it means not even a second prediction with Bolt Strike will beat Slowbro later (though Rocks does make this a bit riskier for Slowbro)
You obviously have not read any of my posts about Mega-Ampharos, whether it be in my Mega-Ampharos discussion thread or earlier on in this thread. Most people know by now that I'm a big fan of physically defensive Mega-Ampharos because of its ability to absolutely hard check any Victini, and counter any set that isn't CB. Obviously, when I see Victini in team preview and I have physically defensive Mega-Ampharos, I'm going to get that mega evo ASAP, maybe even turn 1 if I can. This is basic stuff.
Next is the Pursuit issue. You think that all of Heracross, Honchkrow, and Krookodile can only use Pursuit on Victini? Hell no. Krook and Cross also have Knock Off, so it's a damn big risk for Victini to stay in against them. It's no safer against Honchkrow either thanks to Sucker Punch. Odds are, Victini can't chance this and will be forced out by the sheer threat of a Knock Off / Sucker Punch from these 3, which is why I listed them as the Pursuit users that are best to take out Victini. Because they put Victini in a mind-game. Most of the time, they come out on top.
Also, I absolutely love how you just ignore Stealth Rock. If you see Victini in team preview, this should be one of your first goals; get Rocks up and keep them up to limit Victini's ability to switch-in. Sure it has decent bulk thanks to that base 100 HP, but it isn't going to look so hot at 75% starting out. Sure, it may still be bulkier than some offensive threats at -1 thanks to 100 / 100 / 100 defenses, but the Speed drop can't be ignored either. Anyway, I've elaborated enough. Just gonna leave you with these Mega-Ampharos calcs, which uses the spread you should have used in the first place because this makes sure Victini will have a near impossible time breaking Slowbro, Suicune, and other bulky Waters:
252 Atk Choice Band Victini V-create vs. 248 HP / 252+ Def Mega Ampharos: 127-150 (33.1 - 39.1%) -- guaranteed 3HKO after Stealth Rock
252 Atk Victini V-create vs. 248 HP / 252+ Def Mega Ampharos: 85-101 (22.1 - 26.3%) -- guaranteed 4HKO after Stealth Rock... yikes
As for Bolt Strike and Grass Knot...
252 Atk Choice Band Victini Bolt Strike vs. 248 HP / 252+ Def Mega Ampharos: 31-36 (8 - 9.3%) -- possibly the worst move ever
252 SpA Life Orb Victini Grass Knot (80 BP) vs. 248 HP / 8 SpD Mega Ampharos: 43-51 (11.2 - 13.3%) -- possible 7HKO after Stealth Rock
In short, hope you have LO / Specs Psychic. Am I trying to say Victini isn't a threat? Heavens no. It is a threat. It's A+ for a reason; you need to be ready for it, but it's perfectly capable of being beaten if you know what you should be doing against it.