I created a new fresh world, and right after i died (few mins in game, and within the spawn chunk too), it started to lag extremely, and the lag stayed.

Before I died, the game run very smooth, just untill i died it went off the scale.
And It appeared to gotten worse after following deaths.

• Possibly related: Mobs started turning invisible after the respawning, and framedrop.

EDIT: Game output, attached as requested.