What is the most professional approach to this?
Never lie, don't try to hide something. Just list it as every other experience in your resume. If you feel that the company has a bad public reputation and that this is potentially problematic, add a sentence like "I left because of cultural differences".
Is it acceptable if I put a placeholder name instead of company's actual name?
It may be acceptable, but it will not help. Quite on the contrary, it's about the worst thing you could do: it will draw WAY more attention to this job than any "normal" mentioning would do. Almost every interviewer would immediately try to deep dive into that one.
The question you didn't ask: how to talk about it
This position is likely to come up in any interview so should prepare yourself to talk about it openly, accurately, and confidently. This will most likely require brainstorming many potential questions, carefully formulating the answers, writing them down and memorizing them.
You can of course try to keep it anonymous and refuse to talk about it all. However, this will be a deal breaker for most interviews: you are clearly hiding something and that's not acceptable for most employers. If you don't give them a story, they will make up their own, and it's not going to be a nice one.
Here is the good thing: you haven't done anything wrong and if you handle this well, you can demonstrate your skill in dealing with tricky situations. The key here is to blame the company without bad-mouthing them. Start your story fairly generic and then only add more detail if follow up questions come up. Example:
Q: Why did you leave your last job?
A: Initially I enjoyed working there and there was great technical learning. However over time I felt that there were some cultural difference between the company and myself and I thought it would be best to part ways.
Q: What do you mean "cultural differences"?
A: As I learned more about the internal workings of the company and also the way they interact with customers I felt that their behavior wasn't fully aligned with my own values and personal standards.
Q: Oh wow, tell me more.
A: Sorry, any specific details would be confidential and I need to honor my confidentiality commitments. I'm sure my values and standards would not be a problem here and I'd be happy to talk about that in as much detail as you like.