Evil can be defined in different ways. One simple one from Judeo-Christian tradition is the sin of Greed, and the commandment against same. Insatiable desire for wealth, wanting excessively more than one needs, etc. There is also in opposition to a fundamental principal of Buddhism, and other religious faiths and traditions, including the way natural animals and humans behave (they take what they need, then stop).
My understanding is that corporations whose shares are publicly traded for speculation on (e.g. American) stock exchanges are required to have a dedicated purpose to increase their value, by law. So you have organizations whose purpose is to become more and more valuable – to acquire more and more power and wealth etc., so that the stock value will theoretically increase. So for any amount of profit, wealth, etc., the purpose is to have more tomorrow, and tomorrow, and tomorrow, forever. Whatever value a company has, it’s purpose is to have more in future. In fact, to have as much as it can as soon as it can would be ideal, and this pursuit is treated scientifically and passionately, including applying military and psychological science to the pursuit, including driving competitors out of business, creating needs that people don’t presently have, removing others’ self-sufficiency, owning ideas and DNA and land and politicians and shaping laws to make their business more profitable and… anything and everything.
Essentially, for-profit organizations like that pretty much epitomize greed as far as I can see, which makes them essentially sin engines and evil by most faiths I’m familiar with, with the exception of Capitalism (the faith that there is always more to own and consume, and owning and consuming more is always good).
For non-religious definitions of evil, one might observe that there is only so much that can be owned, at least on this world, and organizations with the purpose to own unlimited wealth, means powerful selfish organizations trying to hoard power and resources, which ultimately (and presently) means depriving others of as much as possible.
Corporation doesn’t equal evil. But for-unlimited-profit corporation… maybe does. It’s the “unlimited” part that’s really problematic, it seems to me.