One who frequently engages in excessive complaining, negative banter and/or a genuinely poor and downbeat attitude. Naysayers are distinguished by their tendency to consistently view the glass half empty, make frequent one-way trips to negative town, and constantly emphasize the worst of a situation. They have the capacity to rant and whine for hours on end about the most insignificant inconveniences. They tend to travel solo, but have the keen ability to spread their pessimistic attitude to a group of unsuspecting bystanders and encourage others to employ their mindset.
Naysayers tend to blend in with those around them rather well, granted they have learned over the years to adapt to their surroundings. However, when the opportunity arises, their true nature will be exposed and they will stop at nothing to exclude others or bring a general sense of negativity to any situation.
Not to be confused with non-naysayers who fight against the negativity brought forth by naysayers, make the best of a situation and are not afraid to call out a naysayer on the spot.

Someone who is possessed by clout chasing. The original human is now gone and a demonic entity that feeds on clout is all that is left. An empty shell with no control of their actions, forced to blindly react to situations they think will bring them attention.

someone with an aggressively negative attitude

a person or group of people who don't agree with your ideas based on their "hater" personalities

a very negitave person

Refers to a person who as a pessimistic view in life and is always looking for excuses for not being able to achieve what others are able to. They complain non-stop and expect the world to give them handouts.

a horse.