Oh, I see what you mean.
Does Golden deck and double Golden deck count? And Goons?
What you helping to point out here is that there's not as clear a line between what is or is not an "alternate win condition" as I was thinking at first. So while no cards use the "you win" terminology, existing cards can cause the game to end instantly with you as the winner if you have met the right conditions.
I think there's two things going on here, "end the game instantly" and "with you as the winner". Dominion already has a lot of "with you as the winner" type kingdom cards, Fairgrounds, nonrushed Gardens, a Monument lead, the Nobles split.
It doesn't have many "end the game instantly" cards, although KC-KC-Militia-Masquerade, Possessed Forge, Goonsing Estates and Curses, Golden deck (doesn't actually end the game, but can create a point of no return for challenging it that functions as an end), and Rats of Great Nobility can. Notably virtually none of these are by intentional and deliberate design. Goonsing Estates is as close as it gets.
A concern for the fun factor on a instant-win card is that maybe it would end the game too soon. Goonsing Estates and Golden deck aren't hated by all that many players, though, because they usually don't end the game too soon. It takes like 5 or 6 Province acquisitions' worth of times to get those going, and then the draw to playing them is that they will be worth more than 5 or 6 Provinces. Iguana's design is similar in that it would appear to take 6-10 Province acquisitions' worth of time to achieve the wincon, depending on the board. So if it's 6, you go for it and it's the best strategy, if it's 10, it's a trap, and either way, the overall game length is reduced, not extended. People usually want the game length extended, 8 Province games are about as short as they can handle. Colony games and Fairgrounds games are good, etc. Which makes sense if you think about 8 Province games having their length optimized for games among inexperienced players, who take so long to acquire them they act more like 10.