If I make a copy with Leblanc Legend at a battlefield and the unit had 2 more might than its original might because of a card effect, after my turn ends does the copy lose the 2 might or does the copy keep the original card might plus the additional 2 might the original had when making the copy?

The [Temporary] Keyword

According to Rule 816, the [Temporary] keyword is a triggered ability that acts as shorthand for: "At the start of this permanent's controller's Beginning Phase, before scoring, kill this." This keyword does not cause the unit to be removed automatically at the end of the turn.

Copying and Might

When you create a copy of a unit, you are creating a new game object that copies the "copyable traits" of the original unit.

• Copyable Traits: These are the printed traits of the card or the traits of the object it is currently copying.
• Persistent Modifiers: Any temporary changes, such as buffs (e.g., +2 Might from a spell) or snapshot modifiers, are not part of a unit's copyable traits.

Therefore, when you make a copy of a unit that currently has +2 Might from a spell or other temporary effect:

1. The copy will possess the original/base Might of the card it is copying.
2. The copy will not inherit the additional +2 Might that the original unit currently possesses, because those modifiers are not part of the original's printed or copyable traits.

Summary

The copy will not keep the +2 Might. It will enter the battlefield with the unit's base Might (as printed on the card) and will remain on the board until the start of your next Beginning Phase due to the [Temporary] keyword.

Note: I could not fully verify the claim regarding LeBlanc's ability preventing the [Temporary] trigger.