When using /kill on an ender dragon, the output is

Killed 9 entities

.

Reproduction Steps

1. Summon an ender dragon, either by going to the end or by using

   /summon minecraft:ender_dragon

   .

2. Kill the ender dragon with

   /kill @e[type=minecraft:ender_dragon]

   .

Expected Output
The chat output would be

Killed Ender Dragon

.

Actual Output
The chat output is

Killed 9 entities

.