Your question could possibly be more vague
In coutries such as Russia or Turkey, president is effectively head of the government aswell, in other euro countries (s)he is merely a figurehead for ceremonial occasions. United States and France fall somewhere inbetween those two extremes.
To be sure, you would have to actually read constituion of said country, as constitution clearly specifies who holds what powers in executive branch.
I wonder how do you define "dictatorial" country, that label is awfully popular today.
If you mean that either Ukraine or Russia is ruled by one dictator without limits, then that is blatantly false.
Russia has quite peculiar power elites, that struggle against each other in the Moscow and Petrograd. Not unlike power elites do the same in Washington. In both countries, president has to expend quite alot of energy on mediating interests of different cliques.
Ukraine is even more complicated as politicians blend with oligarchs and western agents, who keep pumping free money in the country.
Atleast in the first case however, rule of law is formally followed, when power balance requires it, the law is changed. So, take your time and read it