pencil 2 discharging very fast on ipad pro m2 since latest update

Rapid discharge of your Apple Pencil will not be caused by an iPadOS update. It is perhaps far more likely that your Pencil Battery has a fault, or has been damaged through deep discharge.

The tiny internal Li-ion battery is susceptible to permanent/irreversible damage through being left discharged for long periods. Even some “new” pencils can exhibit signs of failure out-of-the-box, especially if they are “old stock”. 

It is essential that if you have an Apple Pencil that you charge it regularly - whether used or not - so as to protect the battery from deep-discharge. Do not allow a pencil to remain in low-charge state for any period of time - as the internal battery will fail, rendering the Pencil useless. Setting aside an unused Pencil, for extended periods, is a recipe for premature death of the Pencil battery.

It is recommended that a second generation Pencil should be docked with its host iPad whenever it is not being actively used - as this will optimally charge the Pencil and protect its battery from damage.

If the Pencil Battery has failed, the only remedy is to replace the Pencil. If the battery has failed and your pencil is within its one-year warranty, you should look to having it replaced by your retailer or at an Apple Store.

If you continue to experience difficulties, you might be advised to visit the Genius Bar at your local Apple Store or Apple Authorised Service Provider (AASP) - where the technicians will be able to test and assess your iPad and Pencil:

Genius Bar Reservation and Apple Support Options - Apple

Same here . My pencil was holding charge after using it for many hours until new Apple Pencil came out . Now it drains in not even an hour . What a disgusting practice