The phrase "unbeatable team" means a group of people who work together so well that they cannot be defeated or outperformed by anyone else. Full definition
They came within minutes of beating a supposedly unbeatable team. (sbnation.com)
Even though they're paleo cookies made with almond butter, they taste very similar to traditional peanut butter cookies, and the crumbly, buttery cookie and creamy salted caramel are an unbeatable team. (acalculatedwhisk.com)
Fix that and keep the offense we had, and you have an unbeatable team. (sbnation.com)