I'm more surprised jynx is still in NU over anything else.
In a tier where spikes are extremely viable with a lack of good rapid spinners, jynx is clearly too much for the tier with its offensive capabilities.
Jynx is very versatile with sets such as calm mind, lovely kiss, fake tears(with sub, 3 coverage moves or lovely kiss) and choice specs. With this versatility there is no clear safe switch-in to it and by the time a player has figured out the jynx set they have likely lost a huge amount of momentum in the match(such as anything that isn't hypno being put to sleep) and could result in the loss of one of the player's party.
Fake tears+spikes vs its 'switch-ins':
252 SpA Life Orb Jynx Ice Beam vs. -2 252 HP / 252+ SpD Hypno: 121-144 (63 - 75%) -- 6.3% chance to OHKO after 3 layers of Spikes
252 SpA Life Orb Jynx Shadow Ball vs. -2 252 HP / 252+ SpD Grumpig: 148-177 (79.1 - 94.6%) -- guaranteed OHKO after 3 layers of Spikes
252 SpA Life Orb Jynx Ice Beam vs. -2 252 HP / 252+ SpD Thick Fat Grumpig: 62-74 (33.1 - 39.5%) -- 12.1% chance to 2HKO after 3 layers of Spikes (beats pig 1v1)
252 SpA Life Orb Jynx Psychic vs. -2 252 HP / 252+ SpD Flareon: 125-148 (72.6 - 86%) -- 87.5% chance to OHKO after 3 layers of Spikes (Sassy flareon doesn't have room for quick attack and only does around 25% anyway)
252 SpA Life Orb Jynx Ice Beam vs. -2 252 HP / 252+ SpD Kecleon: 118-140 (70.6 - 83.8%) -- 62.5% chance to OHKO after 3 layers of Spikes
After kecleon's ability:
252 SpA Life Orb Jynx Ice Beam vs. -2 252 HP / 252+ SpD Kecleon: 58-70 (34.7 - 41.9%) -- 77.4% chance to 3HKO after Leftovers recovery
252 SpA Life Orb Jynx Ice Beam vs. -2 252 HP / 0 SpD Metang: 109-130 (65.2 - 77.8%) -- 18.8% chance to OHKO after 3 layers of Spikes
252 SpA Life Orb Jynx Ice Beam vs. -2 0 HP / 0 SpD Aggron: 136-162 (93.7 - 111.7%) -- guaranteed OHKO after 3 layers of Spikes
Pretty much gurantees a kill.
The revenge kill argument is not foolproof- in order for something to revenge kill it, jynx would have needed to kill something first and if the jynx is behind a sub then this does not matter. If you decide to predict fake tears and go into a pursuiter for example, they jynx could sub and you're pretty screwed and with the majority of pursuiters being weak to ice(fearow,scyther) they cannot pivot into a jynx like a sneasel could have into predicted STAB moves if it was NU. The fact revenge killing is one of the only guaranteed ways to check jynx shows how centralising it is.
Maybe with houndoom being test-banned in UU, jynx might be moving up to UU anyway but I feel it is unhealthy to stay in NU any longer.