So I was playing as Venture defending on Havana and I popped their ultimate then got kills on the enemy Lucio, Mercy, and Widowmaker but the challenge is still incomplete and I have no cute spray for them. It was even the play of the game where it can be seen in the feed that I scored the killing blow on all 3 using the Tectonic Shock attacks, I recorded the play as evidence. The challenge says to get 3 elimination with one use of Tectonic Shock not to get 3 eliminations with one blast so that shouldn’t be the issue here.