You would think e-commerce and cloud computing giant Amazon.com (AMZN), after more than 20 years of unfettered growth, would have run out of room to expand. But the company continues to scout new opportunities. Amazon will try its hand at almost any sort of business, does well at the bulk of them - and threatens to destroy dozens of other companies with its success.

The latest foray into unfamiliar territory? In September, Amazon announced a pilot program for a virtual medical clinic, which includes some in-home services, to be offered to its Seattle-area employees. The virtual clinic aspect would include video visits with doctors, nurse practitioners or registered nurses.

That's not Amazon's first venture outside its comfort zone, either. Amazon also is a grocer, a fashion venue, a peddler of handmade crafts and even its own delivery provider, just to name a few. Amazon has become at best a headache, and at worst a survival threat, for any rival in its path.

Here is a look at 43 companies that Amazon could kill. A year ago, we named 49 such businesses (as well as one it already knocked out). A handful of names dropped off the list - some successfully regrouped, while a few were officially knocked out. Others have been added as they've slipped into Amazon's warpath. Considering Amazon's ubiquitous presence, no company is ever truly safe.

Advance Auto Parts, AutoZone, O'Reilly Automotive

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The unchecked growth of Amazon didn't faze auto-parts suppliers such as O'Reilly Automotive (ORLY), AutoZone (AZO) and Advance Auto Parts (AAP) for a long time. Car parts are too heavy, bulky and specialized to be handled like a consumer-centric commodity. And besides, when mechanics (DIYers or the real thing) need a part to use in a repair, they usually want it quickly. The big three names in the auto parts retailing game haven't needed to worry.

But times have changed, helped along by inventory-management technology and delivery networks that are willing and able to handle goods they simply couldn't before. That's why Amazon was willing to enter the fray in January 2017.

All three stocks have since recovered from their initial setbacks. The underlying companies have finally shrugged off their shock and figured out how to compete with a price-busting Amazon. Advance Auto Parts, for instance, has embraced the idea of in-store pickups of online orders, not unlike the option now offered by many grocery chains.

However, Amazon hasn't yet unleashed its full potential on this front. It's disrupting the auto parts retailing industry gradually, just as it has other consumer-facing markets. Give it time.

Albertsons, Kroger, Walmart Grocery

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Amazon's purchase of Whole Foods Market sent shockwaves through the organic-grocery business. But just as vulnerable (albeit in a different way) are more conventional grocers such as Kroger (KR), privately owned Albertsons and the grocery arm of Walmart (WMT). In fact, a year ago, Amazon was technically the biggest online grocer of the United States, boasting market share of 18%.

That has changed in the meantime. Walmart stepped up its game by growing its curbside pickup option to 2,100 U.S. locations, while Instacart leveraged its relationship with Costco () and Kroger to beef up its share of the market from 4% to 8% over the past couple of