Chavez was a terrible leader who was unable to help his country. Although he was very popular, his economic policies were disastrous. Although his country produced a lot of oil, most of the people lived in poverty. If he had been assassinated, it would have helped the people of Venezuala.
I am Venezuelan, and I opposed the Chavista regime ever since 1999. But as everywhere else in the world: if you kill the president of a country, you're going to have civil wars, revenges, and an even worse economic and social crisis.
Chavez died of cancer, and when he did, the country got sunk in the worst economic crisis of our history under his successor, Nicolas Maduro. Now, let's suppose Chavez was murdered by an opposition-allied killer.
A civil war would've started right of the bat, as Chavez had a HUGE support when he was alive (he aimed to protect the poor and the working class from the oligarchy, the bourgeoisie and the empire, which earned him a huge support in the slums and the poor areas of Venezuela). And no, I'm not taking about something like those "guarimbas" on February 2014: a complete, Syrian-like proportions civil war.
Elections would've been held again, and were probably going to be won by the same party, PSUV, and the same candidate, Nicolas Maduro
The public or private policy of tacit approval of assassinations is a poor strategy. Assassinations create a political vacuum that can lead to anarchy and civil war. No matter how bad a leader of a nation appears to his adversaries, assassination should be a last resort after diplomatic, economic, and military options are exhausted. The policy of assassination may also lead to a reprisal and an assassination of the adversaries leader in revenge.