- Amoonguss did what it usually does for a while, and to some extent it still does that. However, as people realised the power of neutralising mons in SV, "lead Amoonguss" was discovered - it'd run Red Card and just lead off, click Spore, and you didn't have much of a choice but to sack something to sleep. Red Card obviously had the side benefit of being great against Booster Energy users.
- There were a few popular Hypnosis Iron Valiant teams at various points in the metagame. It'd turn beating it with any non-Gholdengo check into a slightly weighted coinflip, Games against this thing got ugly really fast, especially because Iron Valiant is so versatile that you didn't necessarily see it coming unless you knew the team, as opposed to Amoonguss.
- Alolan Ninetales, at its peak, was super high in usage, and a lot of its variants ran Hypnosis. Considering it was supporting the incredibly broken Baxcalibur, it's not hard to see why this would become a problem very quickly, and it's not like Ninetales-A does a ton of damage on its own, so it didn't lose much by clicking it. Its bulk and typing also gave it plenty of fishing opportunities.
- Venusaur's new popularity has led to a decent amount of Sleep Powder sheananigans, which is very dangerous considering its threat level. Hisuian Lilligant has been fringe in OU since it dropped but its antics on Sun teams with Sleep Powder are incredibly frustrating to play around. Brute Bonnet was much the same thing. All of these were also incredibly threatening to everything that could hope to absorb Sleep.
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To address the obvious question of "why not Darkrai?" - we have a few reasons;
a) Darkrai is certainly moving the needle here, but we have seen enough examples of this throughout the generation;
b) Sleep's layers of RNG - between 1 vs 2 vs 3 turn sleeps and whether or not the moves actually hit to begin with - are undesirable regardless of Darkrai's presence;
c) The mod we currently use for sleep is unfaithful to cartridge mechanics, which would *maybe* be okay in exceptional circumstances to keep the game playable (such as the various RBY desync patches on sim), but we do not necessarily feel that this warrants such a mod.
Any and all feedback from here is appreciated. Thanks!