They ruin it for everybody.
真是害群之马
And you had to ruin it for him, didn't you?
还有你，你非得替他毁掉这事，是不是？

tear up 撕成碎片
Few expect to tear up their rulebooks.
几乎没有人有撕毁自己规则手册的打算。
I suggest that you tear up the composition and start over again.
我建议你把这篇作文撕掉，再从头开始写。