Riot Games recently added new finishers in League of Legends which would activate strobing lights that turned out to be dangerous to people with photosensitive epilepsy. Riot initially didn't plan on removing it but changed their mind.
League of Legends features several flashy elements that could potentially cause issues to people with photosensitive epilepsy. According to one such player who goes by Apricot Princess on League of Legends forums, most of these elements could be avoided.
For example, banning Lucian and Lux solved most of their problems since not many other champions have flashes similar to those of Lucian's Q or Lux's ulti.
All of that changed when Riot Games introduced the new finishers right before MSI 2019. These Trials finishers that represent the killer's chosen house have strobing lights that triggered photosensitive epilepsy and since they were available globally, they couldn't be disabled.
Initially, Riot's response to the thread was that the company didn't have time or enough engineers to introduce a toggle button that would allow epileptics to disable the flashy animation. Naturally, this didn't sit well with the community and a backlash occurred not long after.
This seems to have pressured Riot Games into actually taking action and they decided to remove the finisher animations until further notice. The developers will try to give players an option to toggle the animations off in the meantime. Both the original response and the updated one can be seen on Riot Xenogenic's post on the official League of Legends forums.
Considering the finishers were rewards for an event themed after MSI 2019, the players who already attained them would likely feel they lost their progress but Xenogenic reassured them that compensation would come along.
League of Legends isn't the only game that could cause epileptic seizures - Ubisoft's games often contain the epilepsy warning as they load up. Riot's game did not.
Given that epileptic players are at a disadvantage because they have to ban certain champions simply due to their ability animations, such a warning would be the least the company could do. Or as the players already suggested, a photosensitive mode would make more sense.