Idiom to be used as replacement of “A coin has two sides”

As you can imagine, the phrase you might use would vary depending on the identity of ABC.

Your original line, written as close to the original but corrected for grammar and meaning. It’s still a bit clumsy, but not exceptionally so:
“As we know, there are few things in this world that do not have two sides; ABC also has both pros and cons.”

Here are a few that came to mind, including the sort of context in which they might be used.

Black and white
Generally for a moral issue, particularly one you may have been arguing strongly for or against, but now want to introduce the opposite position. This almost always used in the negative (“not black and white”.) It means that a wise opinion on the matter is not simple (black or white), but contains “shades of grey.” (That’s another good idiom that almost applies to your question.)

ex: “I’ve been telling you about the ruthless behavior of the guerrilla forces, but honestly, the issue isn’t black and white, the government in this area has been committing crimes against its people for decades.”

Two sides/two-sided
This means much like your two sides to every coin idiom, but it can be applied much more broadly. I would use this if I were talking about an argument between two people or organizations who had opposite points of view.

ex: “Mr. Smith says that his wife left him because she didn’t love him anymore, but every story has two sides; she claims that he had a mistress.”

This is not an idiom, but it is a wonderful word that means very much what you are searching for. A gem is cut with many facets that sparkle. Something that is multifaceted can be looked at from many points of view, with each point of view showing something new. It’s generally a positive adjective when applied to people, not necessarily so when applied to events. It’s not usually used for objects (except gems, perhaps, in its literal form.)

There’s no such thing as a free lunch.
This is used after describing the many wonderful qualities of something, just before you lead into its costs. It could also be used derisively by someone who doesn’t believe the wonderful things he or she is being told. Though it could be used to indicate that the financial cost of something will be high to compensate for its many wonderful qualities, it is typically used to indicate a significant negative quality other than high price.

ex: “The newest model electric cars use batteries that are cheaper, lighter, and last longer than older models’ batteries. However, there’s no such thing as a free lunch, and these batteries contain a wide range of toxic compounds that sometimes explode.”

ex: Bob: “If you buy this car women will want you and men will want to be you. It costs less to operate than your current car and I can have you driving it today without any downpayment.”

Jim: “There’s no such thing as a free lunch. What’s the catch?”

(“What’s the catch?” means “What are you not telling me?”)