One of the challenges for the Tenrai events is stopping enemies on a killing streak five times. I’m sure if you put in a lot of time and/or get extremely lucky, you will get it done just by playing naturally, but it’s still an atrociously designed challenge.
First of all, it’s entirely out of players’ hands. I do have no control over how good my enemies are and how many kills they get. Challenges are supposed to be something you can specifically try to achieve instead of hoping it happens randomly, especially if said challenge is essential for progression.
The second problem is that a challenge like this gives me an incentive to play poorly, ignore my teammates, and completely ruin my team’s odds of winning.
As for suggestions, changing it to “go on a killstreak five times” would already be better, even if still rather challenging. Preferably though, I think such time-limited events should have challenges that incentivize you to play the mode without forcing you to commit too much, so double/triple kills would be more reasonable.