Beware of the warden.

warden stats:
height: 4 blocks
speed: slow (for now)
strengths: block breaking, gets progressively faster when you damage it, lotsa health, can two shot a player w/ full netherite (non enchanted)
weaknesses: instead of eyes, it has a sensor that detects movement and will chase you. dont be scared though, there is a chance it will walk right by you if you dont move.

About how many hits does it take to kill it with an iron sword?

rewards for defeating it: a chest with stuff inside. whatevers inside i have no clue