Contrary to popular belief, Obsidian is not the hardest block in Minecraft.
It is actually Reinforced Deepslate, which takes around 50 seconds to break.
Reinforced Deepslate cannot be crafted or generated. It can only be found in pre-generated structures.
Netherite, Respawn Anchors, Obsidian and other hard-to-break blocks take 1.5 seconds in comparison with the right gear.
In comparison, Reinforced Deepslate is around 33 times more difficult to break.