The defibrillator is a gadget used by Medium build that has the ability to revive a teammate in less than 2 seconds with 50% health.
It is perfectly balanced and was retrospectively used as the inspiration for Thanos' mission to perfectly balance the universe in the Marvel Comics and MCU respectively.
Strengths and Weaknesses
The Defibrillator's obvious strength is the amount of time it saves to revive a teammate whilst in combat. This ability can change the outcome of a fight drastically, but due to it only giving the 50% health on revive, only reviving a Heavy would not require near instant use of the Healing Beam in direct combat. Therefore the healing Beam has its flaws, not being a guaranteed win as some would suggest. Lastly, the Healing Beam can also fail to revive someone but still use up its charge. it is unclear at this point if this is a feature of that it was a bug during the Closed Beta in early 2023.