The only company that leaps to mind that acts like they are actively afraid of Microsoft is Valve. It's the only explanation for keeping the SteamOS alive I can think of (and developing it in the first place, for that matter), and the way it has neither been shut down, nor really given the push it needs to succeed. It's insurance, and as long as it's a half-viable insurance policy, it's doing its job.

Everywhere else, either Microsoft is still the underdog against some very strong incumbent or incumbents (Azure, mobile), or the competition is a decade-old corpse (Office).

Valve isn't afraid of Microsoft, they're just critical of their motives. Steam will always be the destination for digital PC games and there's nothing Microsoft can ever do to change that. Everytime Microsoft has tried to challenge Steam they've failed spectacularly. Microsoft and PC gaming just don't go together.

I'm assuming this was said because people tend to be afraid of growth (eg Uber eating taxis).

But there's something to be said for being scared of companies that have already grown and are stable too. Or at least wary.

Microsoft in the old days used to drive a lot of competitors out of business.

That was part of my point. If you're a 600 pound gorilla, then you don't always need finesse to beat a hundred pound competitor.

So, which companies are people afraid of today then?