Basically every XP badge in this game can be attained when putting in the effort and skill, however there is one notable outlier: The golden multi KO. This badge is extraordinarily rare and is impossible to force by playing well since it relies on sheer luck where almost every factor that contributes to it happening is outside of your control.
While there are some other badges that are also partially not within your control, the situations leading up to them happen often enough that the badges can be reasonably attained. The golden multi KO is a crazy outlier. In my entire time of playing this game I have only ever gotten 4 kills on the enemy bank within 2 seconds once ... and my playtime is approaching 500 hours.
Either reduce the amount of KOs needed from 4 to 3 or increase the time that you have to kill 4 people. 4 players being close together anywhere on the map is already extremely rare and if they are there is most likely someone who has full health and there is no character in this game that can kill another character in 2 seconds.
Maybe do it like this:
- Multi KO: Kill 2 enemies within 2 seconds
- Golden Multi KO: Kill 3 enemies within 5 seconds
- Platinum Multi KO: Kill 4 enemies within 10 seconds
While this would still be rare, it would make these badges significantly easier to attain.