What is the Strongest Combat Item or Tool?

The most strongest combat item or tool is an enchanted netherite axe.

You can enchant it to have special effects, to be stronger, but netherite itself is super strong (stronger than diamond!). Netherite is hard to find/craft. You have to craft gold ingots with Netherite scraps to get one netherite ingot. Netherite scraps are hard to get, because they are crafted from ancient debris, found in the Nether.