I want to abandon a region so that it will be considered uncontrolled for the use of a tactics card, I can't move the units out because its the last season of the game and it is an activated space. Can i voluntarily destroy my own units occupying the space???

Does not say you can choose to disband units whenever you want in the rules, so that means you cant unless there is a rules error, in which case only rule support will be able to answer this.

Now you do have opportunities when you are forced to or have the choice to disband units (if you overstack units over 8, when winter comes and you starve units, or if you want to recruit new units and dont have enough available,) then you can disband some to add them somewhere else.

Component Limitations
If players run out of activation tokens, damage tokens, defeated
hero markers, infl uence tokens, or training tokens, they should
use a suitable replacement (such as a coin or bead). All other cards,
tokens, and fi gures are limited to those provided in the game.
If a deck of cards runs out, players should shuffl e the deck’s
discard pile to create a new deck.
If a player wishes to recruit a unit but all of the units are already
in play, he may voluntarily destroy one of his units in any friendly
area before recruiting. If a player wishes to build a stronghold or
development but does not have any available, he may voluntarily
destroy one of his strongholds or developments in order to build
it elsewhere. If a development is ever left in an area without a
stronghold, the development is destroyed.
These are the only times a player may voluntarily destroy his own
units, strongholds, or developments. This does not include when a
player is forced to destroy units due to unit limits.

Thanks for the great replies