"Unblockable attacks" refers to moves or strikes in a game or fight that cannot be defended or protected against. They are attacks that opponents cannot block or counter with their usual defensive techniques. Full definition
In particular, the various nasty animals inhabiting the islands have nothing but unblockable attacks. (wolfsgamingblog.com)
If it is used mid-way through a fight, your officer will deliver a powerful unblockable attack against the person with the icon on their head. (squarexo.co.uk)
Spreading multiple damaging conditions on a low recharge unblockable attack is potentially very powerful. (dulfy.net)