Which state of Itachi we talking about here? When he is sick or when he is under kabuto control? Or when he break free from Kabuto.

If both of them are in Edo Tensei state, physical damage is useless so Itachi will win here because he has Totsuka Blade while 3rd Raikage don't have any powerful sealing jutsu in his arsenal.

If both of them are not in Edo Tensei then you need to pick which state Itachi are in because Itachi only has 2 stages beside his Edo Tensei : His anbu state after he deleted his clan and his sicked state when he fought Sasuke. You can easily see that both of Itachi's states are pretty young compare to 3rd Raikage's prime state. While we don't know anything about 3rd Raikage at any state beside his prime. It's not fair to compare Itachi to 3rd Raikage because we don't know how strong Itachi in his prime if he is not sick. So ofc a young shinobi like Itachi if encounter 3rd Raikage in his prime will lost.