Bloon Embiggen on multiple cheap bloons provide the greatest value of this card. If used on swarms of 0-delay bloon cards, Bloon Embiggen can act as a finisher, or at least cripple the opponent.
If possible, use Bloon Embiggen onto swarms of Bloons on the turn just before they leak, instead of during the same turn, in case the opponent could afford a board clear.
Red Bloon Storm takes advantage of the Bloon Embiggen's health boost. If the Reds remain undamaged, a full Red Bloon Storm is a complete OTK.
Bloon Embiggen is often used in swarm aggro, and as a combo with swarms, especially with Amelia who can make this Power free with her Act of Power.