The latest android update sucks! Draining my battery like crazy, how do I undo the update?

[Android Central Question]

The last android update this week was a HUGE mistake.
After the update, my battery drop like crazy, a fully charged phone won't even last until 5PM, whereas everything remain the same, last week my battery could last until midnight.

This is the WORST update ever, how do I undo this update?

 

[SpookDroid]

Unfortunately an OS update cannot be undone. Even factory reset, once updated, will stay in that original version. Only way to 'go back' to another version is to flash an older ROM for your specific device.

 

[Golfdriver97]

What phone do you have? How long ago was the update? Sometimes an update has a new kernel packed in and the phone needs to relearn everything. This can take a few days to subside.