Apple Watch Series 9 battery drains quickly and has display issues after the watchOS 11 update

Did you try to unpair it, set it up as a new device and disable the Live Activities as well?

This helped some users.

Unpair and erase your Apple Watch - Apple Support

Set up your Apple Watch - Apple Support

Let Apple know directly about your issues after installing watchOS 11 by using the Feedback link.

This is the only way to reach them, since they do not follow these user to user communities.

Feedback - Apple Watch - Apple

watchOS 11.0.1

This update includes bug fixes for your Apple Watch, including:

Apple Watch may unexpectedly restart for some users

Music app may unexpectedly quit when loading media

Battery may drain more quickly than expected

Touch screen may be temporarily unresponsive for some Apple Watch Series 9, Apple Watch Series 10, and Apple Watch Ultra 2 users

Messages may unexpectedly quit when replying to a message with a shared Apple Watch face

I just updated to 11.0.1 and now my battery on the series 9 apple watch drains

completely. I did go in and tried to turn off a bunch of stuff... before that, when

messages came in the screen would freeze and I would have to go to the watch face

and recheck to have it clear. That freezing seems to have been fixed but the battery

drains terribly over night now ... I may have to leave it on the charger over night ... I hope

they fix this....... I have been happy with this, my first apple watch ever.

Same here. Battery drains quickly and does not charge completely after leaving on charger all night.