February 16 nuke
The February 16 nuke (or February 17 nuke depending on where you live, also 2/16 and 2/17) was a mini-nuke that started on February 16, 2021 at 4:13 PM PST (7:13 PM EST, 00:13 UTC). An exploit with Dyno was discovered that resulted in 40 @everyone pings, until the server was locked down 8 minutes later.
Cause
The ?nuke command (ironic right) had just recently been created. The command output "
Banning users... {user parameter}/6700". However, when the command was being created by Luq, the syntax {noeveryone} was not added and the disable everyone box was not ticked, meaning that, if the user paramater was an everyone ping, it would ping everyone.
While Caskain was browsing through changelog, he noticed the command was active. He did "?nuke @everyone," not expecting it to work, however it did :badluck:.
The Nuke
The exploit was first used at 4:13 PM PST (7:13 PM EST, 00:13 UTC) in the #casual channel. It quickly spread to all other channels. This resulted in alive chat dx
Only admins had the power to truly fix the issue. Mods tried their best to help, but the only thing they could really do was lock the channels this was happening in. But once one channel got locked, people just moved to another. There were 40 @everyone ping exploits in total, plus 1 more by Soapkiller in #announcements 
Weezor and Luq were both offline at the time. That left Soapkiller as the only admin that could step in, but even he was on Do Not Disturb. His first message was sent at 4:19, but with Soap being the laziest admin, he didn't do anything at first. Dyno got kicked at 4:21, which prevented any further exploits from happening, but also left the mods unable to unlock any channels. With every channel being unusable, VCs got very crowded very fast. Soap re-added Dyno at 4:27. #general was finally unlocked at 4:32, and other channels followed later.
Aftermath
Like 100 people left as a result of the incident.