Outdated: pre-v1.18.30 only
ExpertCoder14’s answer is better for v1.18.30 and up.
You can use /clear
/clear
<player> netherite_sword -1 0
. The -1
matches all data values and the 0
specifies the maximum number of items to clear (so none will be cleared). If the player has at least 1 netherite sword in their inventory, the command will output a success.
The success can be detected using a chain command block. Put the /clear
any command block facing a conditional, always active, chain command block with the command that you want to execute if the player has a netherite sword.