Mortal Kombat X
73 Achievements
1,500
61-82h
Can't Stop This
Win an Invasion 1v1 fight
5
6.46%
How to unlock the Can't Stop This achievement in Mortal Kombat X - Definitive Guide
These still work in January 2024. The event seems to be on a weekly basis, but the day of the week is random and they usually last for 24 hours. If you check in each day once under the Faction menu (Invasion Boss & Invasion Tower become active), you will hopefully find a point where an invasion is active. Alternatively on TrueAchievements you can check the "Recent Winners" tab on the right per achievement, when viewing the website in desktop mode, where you might notice if someone unlocked the achievement on the current day. For example in January 2024 the Invasion event was available on the 5th, 11th, 16/17th, 25th.
For this achievement, as the other guides describe, you can play "Single Fights" under the "One Player" menu or "Living Towers". After around 3-6 fights you should get a prompt at the end of the match informing you that an assassin wants to attack. Accepting the event will start the fight against the invasion assassin. Keep in mind this match will also be just 1 round if you have that configured in the settings. Winning the fight will unlock this achievement. In my case the achievement didn't unlock right away, only around 1 hour later, but that's probably a bug from Xbox.
Additionally, since the Invasion event is time-limited keep in mind that this is also the only time you can work on the following event related achievements:
Invasion 1v1 fights are only available during an active Invasion event. To see if there is an Invasion in progress, you can check the Faction section of the main menu. Unlike the other Invasion related achievements, you do not have to be actively playing an Invasion game type to be challenges to an Invasion 1v1 fight. At anytime during an active Invasion, you can start up playing some 1v1 matches or a living tower and you should receive a message telling you about an Outworld assassin. You will be given the option to either except or decline the fight; accept the fight and win to unlock the achievement. It may take some time for you to be challenged so just keep retrying matches until you get one to pop up, they seem to be a fairly regular occurrence during invasions so you shouldn't have to wait too long.
It only works when Invasion Mode is currently online. To check if it's available, you first need to select the Online option in the main menu. This is to gain access to the online portion of the game and get connected to the servers. Now that you have access to the servers, go back to the main menu again and select the Faction option and see if Invasion mode is enabled; otherwise you need to come back later.
According to Panicore, the secret fight shows up more times if you keep playing Hourly Living Towers.
https://www.youtube.com/watch?v=ToMs23Rj9Qo
Credits: Panicore