for the better
: so as to produce improvement
The new policy is a change for the better. [=the new policy is an improvement]
My father's health has recently taken a turn for the better. [=has recently improved]
a change for the better/worse
a person, thing, situation, etc. that is better/worse than the previous or present one
Voters see the new leader as a change for the better.
I reckon we've all made a big change for the better.
See also:for the better · Everyday English