Step 1: Think about electrical conductivity as a clue.
A solution conducts electricity well only when it has plenty of free ions floating in it, so how completely an acid breaks apart into ions can be judged by how strongly its solution conducts current.
Step 2: Compare the mineral acids in the list.
$\text{HCl}$, $\text{H}_2\text{SO}_4$, and $\text{HNO}_3$ are all classic mineral acids that hand over essentially every one of their acidic hydrogens to the water, so their solutions are excellent conductors, meaning near total dissociation.
Step 3: Now look at acetic acid. \[ \text{CH}_3\text{COOH} \rightleftharpoons \text{CH}_3\text{COO}^- + \text{H}^+ \] The double arrow itself is the giveaway, it shows an equilibrium where only a small fraction of molecules, typically under $5\%$, actually split apart, the rest remain as intact, un ionised molecules.
Step 4: Draw the conclusion.
Because acetic acid only partially ionises while the other three go essentially all the way, acetic acid is the exception that does not dissociate completely. \[ \boxed{\text{CH}_3\text{COOH}} \]