Does Unchecked Power target?

No, Unchecked Power does not target.

According to Rule 352.10.d, a game object mentioned in the text of a spell is a target unless it is programmatically selected based on its characteristics rather than chosen by the spell's controller. The rule explicitly provides the following example:

• "Kill all units at battlefields" doesn't target anything.

Because Unchecked Power affects all units at all battlefields simultaneously rather than requiring you to select specific units, it does not target. Consequently, it bypasses effects like Deflect that require a spell to target in order to trigger.