"Counter vails" refers to the act of opposing or nullifying something. There are multiple synonyms that can be used in place of this phrase, including counteracting, negating, neutralizing, balancing, offsetting, and countering. These words all convey the same idea of canceling out or balancing the effect of something else. Depending on the context of the sentence, one of these synonyms may be a better fit than "counter vails." It's important to choose the appropriate word to ensure clear communication and convey the intended meaning. Regardless of the synonym used, the overall idea is to diminish or eliminate the impact of something.