If you are the only one in the entire community doing so, then it wouldn’t help all that much - though good on you to be so considerate!:-) But it’s not required, and I don’t think I’d use the NSFW marker for this, if it were me. You could rather use a hashtag or some such for maximum friendliness? e.g. “[violence]”, to allow people to use filtering keywords (for those that use apps that even support that - I don’t use apps so I don’t know which ones can do that).