Better Ping Display Wiki & Guide
wiki.9minecraft.net/better-ping-display-9minecraft-mod/
How Better Ping Display shows each player's exact ping as a number in the tab list, colours it by latency, and can be configured.
Overview
Better Ping Display replaces the small five-bar connection icon in the multiplayer tab player list with each player's exact latency, written as a number in milliseconds.
The change is purely visual and happens entirely on the client, so it works on any server without the server needing the mod. Open the player list the way you normally would (by default, hold the player-list key) and every player's ping is shown as a number next to their name.