tip the balance/scales idiom (also tilt the balance)
打破平衡局面;起决定性作用
If something tips the balance or tips the scales, it is the thing that causes a particular situation to happen or a particular decision to be made, when other situations or decisions are possible.
The teams were evenly matched until two quick goals from Rooney tipped the balance in favour of England. 两队本来势均力敌，直到鲁尼很快攻入两球，形势开始变得对英格兰队有利。
She was a good candidate, but her lack of computer skills tipped the scales against her. 她本来是个不错的候选人，但她缺乏计算机技能，这对她很不利。