When players chat "nt" in Valorant, it means "nice try". It is a term used not just in Riot games title but is also common in other games. Players usually use this term when one of their teammates or a lone player fails to win a clutch situation despite giving notable efforts.
This gives positive reinforcement to the remaining player and the team in general. Saying "nt" via chat or voice goes a long way and helps your team as a whole!
Spreading toxicity won't help as it may result in players getting tilted, getting mad, raging, or they may end up throwing the game!
In the past, most other multiplayer games such as first-person shooters like Quake (boomer shooter) used the term "n1", meaning nice one.
These days though, all the popular games zoomers play use "nt" or nice try as a way to spread positivity!
Here are a few scenarios as well where "nt" is applicable:
When the last lone player on the team is in a clutch situation, all the other players are watching them try to defuse the spike, they did everything they could and gave notable efforts to try to win, however, they die close to the end.
Teammates spamming NT in your chat and other positive affirmation so you won't get distracted from toxic messages coming from your enemies or maybe someone from your team.