These are the skins for League champions that are advised against due to their potential self-destructive nature.
Xayah Samsung Galaxy
One of the skins honoring Ruler and the Samsung Galaxy team, but Xayah SSG skin is heavily criticized in the League community. While visually appealing with the signature blue-white colors of SSG and a cool appearance, this skin is labeled as 'pay to lose' due to a seemingly 'buggy' transformation effect.

Specifically, League players using this skin report that when activating the transformation animation, when Xayah is returned to her home base by the chariot, there is a streak of light that passes through. And this streak of light, whether intentionally or unintentionally, closely resembles the energy flash effect from Diana's Q - Crescent Strike ability, startling players and canceling their transformation back. However, overall, this is still a decent skin and not excessively 'pay to lose' if players are accustomed to the effects it brings.
Cybernetic Kassadin
One of the most glaring 'pay to lose' skins in LoL has to be Cybernetic Kassadin. Since its release, this skin has been criticized by gamers because his ultimate ability - Void Rift - is as obvious as a sore thumb. Players could easily predict Kassadin's appearance beforehand, rendering his ultimate useless. Despite community complaints, Riot has yet to make any adjustments.

This is truly a bold move by Riot, stripping away the element of surprise from Kassadin's Void Rift. Particularly, in skirmishes, opponents can easily anticipate Kassadin's moves and completely neutralize him. Despite the outcry from the LoL community since its debut, Riot has remained indifferent towards any modifications.
Void Rift from Kassadin is easily predictable when using Cybernetic skin
Cosmic Miss Fortune
As one of the rare Supreme skins released by Riot, Cosmic Miss Fortune perfectly encapsulates both design and the beauty of Miss Fortune. However, alongside its steep price, this skin has garnered criticism for being a true 'pay to lose' outfit, especially when interacting with the champion Sylas.

Specifically, according to the clip analyzed by Vandiril, when Sylas steals Miss Fortune's R - Bullet Time by default, everything remains normal. But when he steals from Cosmic Miss Fortune, Sylas's Bullet Time lacks its usual visual effects. Not only does it not buff himself at all, but this skin also strengthens the opponents. And perhaps everyone understands why, until now, very few gamers or pro players use this Supreme skin from Riot.
Sylas stealing R from Cosmic Miss Fortune lacks ability visual effects
Terrorblade Tryndamere
Similar to the aforementioned skins, Terrorblade Tryndamere boasts a stunning appearance, resembling warriors cursed in movies. However, its overly modern effects actually 'harm' Tryndamere and the newly released skin itself.

Specifically, some gamers have noticed that Tryndamere's Terrorblade skin features a red circle effect under his feet when he uses R - Undying Rage. Especially, this red circle gradually disappears over time of Undying Rage's usage. In other words, players can observe the red circle under Terrorblade Tryndamere's feet to gauge the duration of his attack.
Tryndamere's Undying Rage ability effects are clearly visible through the red circle under his feet
Certainly, during combat, few pay attention to Tryndamere's ability duration effects. However, it's undeniable that this is a way to 'assist' opponents in countering Tryndamere effectively, inadvertently added by Riot in the attire for the champion from Freljord.