My issue is that I need a first paragraph buffer before I break the bad news to a superior. Any suggestions?

My experience is that good superiors like negative messages to the point, and with a rationale. I wouldn't sugar coat it. If it needs sugar coating, get a new job.

Beginning paragraph: To the point...as in
Now there is a downside that I see... or One thing that needs attention is ....

Then offer rationale. If you are full of beans, the supervisor, if he is worth his salt, will tell you.

You did not say what the prob was so just in general this is what I use. With any type of letter written to a superior, the 1st paragraph should be positive. Things that you like about the business, job, whatever they are supervising, things that you have learned and appreciate. The middle of the letter should explain the problem or bad news. The end of the letter thanks him and explains that you would be available to discuss the issue at hand in order to solve a problem, or mend any concerns etc.

I would like to know if it would be appropriate to write a negative message in a memo form or letter form. what is the different

Certainly! When it comes to delivering bad news to a superior, it's important to approach the situation with empathy, professionalism, and clarity. By starting off with a well-crafted first paragraph buffer, you can set the tone for the conversation and provide context that can ease into the difficult news. Here are a few suggestions for creating that first paragraph buffer:

1. Begin by expressing appreciation or acknowledging the positive aspects: Start off by thanking your superior for their time and for the opportunity to discuss the matter at hand. You can also mention any positive aspects or achievements related to the situation to build a foundation of goodwill.

2. Provide a brief summary of the overall situation: Present a concise overview or background information about the topic that you will be discussing. This allows your superior to get a clear sense of what to expect and helps them mentally prepare for the upcoming bad news.

3. Offer reassurance of your dedication/responsibility: Assure your superior that you take your role seriously and that you have thoughtfully considered the issue. Emphasize your commitment to finding solutions or alternatives, even if the news may not be what they were hoping for.

Remember, the goal of the first paragraph buffer is to set a respectful and open tone for the conversation. It should gently transition into the topic of the bad news while showing your professionalism and empathy.