以致 / 以至于【yǐzhì / yǐzhìyú】

以致 opens the second clause and says what the situation in the first clause led to. The result is almost always one nobody wanted – an accident, a failure, a loss – and the cause is often a fault. It is written and formal.

以至于 is a common variant with the same meaning in this use, a little less formal.

Good results take something else

A good outcome sounds wrong after 以致. Use 从而 for a result someone worked for, or plain 所以.

• × 他每天练习，以致说得很流利 → 他每天练习，从而说得很流利
• × 天气很好，以致我们去了公园 → 天气很好，所以我们去了公园

以致 and 以至

以至 without 于 also means "up to, down to" in a list or range: 一年、两年以至十年 "a year, two years, even ten". 以致 never has that sense.