Identifying a published error Hypothetical:


I found an error which fundamentally kills a published paper and re-opens a number of problems the paper claimed to solve.
Not only is there an error, but the results are actually wrong.  Part of another publication (by a different author) proves this.  Yes, I am 100% sure. Other experts have confirmed this in private communications with me.   
I have nothing new to add, other than I can show the second paper proves the first paper is wrong.  
I get no response from the first author when I let them know about the error.  


What is my next step? 

(A) contact editors of the journals with the incorrect results? and then what happens?

(B) post a paper to ARXIV? 

(C) submit a paper to a journal? 

(D) wait, do more research, and try to craft something more "substantial" for (B) or (C)

(E) do some or all of the above simultaneously? (please specify which ones)

I am not sure if my contribution thus far warrants (B) or (C), but I would like to receive some acknowledgement in print.  

Something must be done because this error if unacknowledged will have a negative effect on future research.
I have nothing new to add, other than I can show the second paper proves the first paper is wrong.

If the second paper already refutes the first paper, then there is nothing to do. If you could write a brief, non-trivial paper explaining how the second paper refutes the first (and the consequences of this), that's a different matter.

(A) contact editors of the journals with the incorrect results? and then what happens?

This may be field-dependent, but in general, I think this only be appropriate if the authors acted in bad faith (and thus the paper needs to be forcibly retracted). In this case, it sounds like the authors were simply wrong, so I wouldn't get between the authors and the journal.

(B) post a paper to ARXIV?

Particularly in math and physics, all papers are posted to arXiv. It's not a bad policy for other fields as well (I post all my machine learning papers to arXiv). But it sounds like your results are significant enough that you should publish them in an actual journal or conference, not &quot;just&quot; the arXiv.

(C) submit a paper to a journal?
(D) wait, do more research, and try to craft something more &quot;substantial&quot;

If you have enough &quot;substance&quot; to publish now, then I would go for it (and post the paper to the arXiv while you're at it). If not, doing more research is necessary -- you shouldn't publish a bad paper, particularly one that &quot;calls out&quot; another paper (all the more so if the other paper is well known).