I am looking for a single word that is either a noun (like 'liar') or an adjective (like 'talkative') for a person who always has to have the last word in a discussion.
A single word that means or describes a person who has to have the last word in a discussion
1The best I can offer is that he has "ocd," which means an anxiety disorder in which people have unwanted and repeated thoughts, feelings, ideas, sensations (obsessions), or behaviors that make them feel driven to do something (compulsions). The key is to focus on "feel driven to do something."– vickyaceJun 4, 2016 at 18:05
related: english.stackexchange.com/questions/46627/…– USER_8675309Jun 6, 2016 at 21:59
1"The guy who always has a comeback after I give the authoritative answer."– Hot LicksJun 7, 2016 at 0:50
Members of 'the red team'; 'type-A'; competitive.– MazuraJun 7, 2016 at 1:31
As mentioned in this answer here, one-upman is regarded as an acceptable word. A use case:
Don't bother arguing with Phil, he will always try to one-up you.
However, this doesn't really embody "a person who always has to have the last word." There are several other words that having the last word might be a symptom of, like stubborn, know-it-all, or egocentric, but again, being a last-worder is but a symptom of these traits.
Perhaps, if this person always needed to get the last-word in under their breath, we could call them an ultimumbler, a combination of the Latin word ultimum and the English word mumble.
While I do like saying ultimumbler, it looks horrendous on my screen.
An outtalker. Some definitions for outtalk:
To talk more, longer, or louder than (someone)
Outdo or overcome in talking