Apple

I don't care if anyone has a Xiaomi, Oneplus, Samsung, etc. Each brand is using a modified version of Android, and they chose to be compatible with each other. But for example the "blue vs green bubble" drama is a thing specifically because of Apple locking their unsuspecting users into a closed ecosystem. And it sure isn't Android's fault for not being compatible with it.

The more power a company like this gains, the worse will it be for the whole industry.