Wait until you find out how much exposure you get by being outside in the sunlight surrounded by cell phone towers.

Communication is bidirectional so there is no need for the downlink to be more powerful than the uplink: the phone must be able to send data to the satellite using its own antenna and battery.

However in theory a more powerful downlink could send data down to the phone faster than the phone sends it up to the satellite.

A really powerful satellite has a power supply of about 1 kilowatt.

Assuming perfectly efficient antennas and a single spot beam with a diameter of about 300 kilometers (realistically, it's going to project dozens of these for a total of several thousand kilometers, but let's stick with the worst case here), that's an area of about 200 000 square kilometers to cover with that one kilowatt, i.e. 5 milliwatt per square kilometer.

This is roughly the same amount of maximum EM radiation emitted by a single AirPod – now spread that over one square kilometer.

Compare that with a regular LTE or 5G cell with a cell radius of at absolute best 30 kilometers (but often much, much less, e.g. 1 kilometer) and an unusually high EIRP of 50 watt, and you get 17 milliwatt per square kilometer. Or take an AM radio station: These transmit with 50 kilowatt and are much closer to people, sometimes located on rooftops in densely populated cities.

Realistically, what arrives down on earth is probably still a few orders of magnitude less than that and just at the edge of the noise threshhold for the phone. It's not exactly a beam weapon.