Fidel Castro has had an enormous impact on the geopolitics of the era in which I have lived, an era of increasing U.S. imperial economic/military dominance of the globe. As with all highly influential leaders he has his avid followers and his keen distractors. His legacy is somewhat more mixed, but in general, and from an international globalist perspective, he accomplished more positive than negative, in particular in light of the lifetime U.S. embargo/sanctions against Cuba.
The latter is very interesting when considering the U.S.’ relationship with dictatorships/autocracies around the world. Having killed off several millions of Southeast Asians and over 50 000 of its own people during the Vietnam war, the U.S. is now actively trading with the minimally communist Vietnamese government as if nothing ever happened. China, which is labelled a communist dictatorship, is in effect an integral part of the U.S.economy, without which the ordinary consumer citizen of the west would not be able to buy so much cheap/inexpensive stuff for their entertainment. Millions died in China, both as a result of western nations trying to slice the country up into spheres of influence, and following because of Mao’s reactionary policies. 
Canada has taken a slightly different approach, never having cut diplomatic relationships with Cuba and recognizing mainland China’s government in 1970, nine years before Nixon did for the U.S. U.S. president elect Trump has called him a “brutal dictator” who has “killed tens of thousands” (more like two thousand), imprisoned political activists, and not allowed free speech. There are many detractors of Castro in Canada. In consideration of what I have said above he has been considerably less brutal than the U.S. in its actions (generally supported by Canada) around the world in its invented fights against communism and now terrorism.
All empires need enemies of the state in order to redirect the anger of their own citizens outwards towards an evil other. Cuba effectively serves that purpose for the western hemisphere – a supposedly evil example standing up to the good empire. The U.S. agreed with Soviet Russia not to invade Cuba after the 1963 nuclear standoff, but there certainly have been many other inept attempts to do away with Castro, perhaps half-heartedly as that would remove the evil other from the U.S.’ back yard – Latin America.
Neither the U.S. nor Canada, of course, are concerned about relationships with a country simply because they are a dictatorship. Saudi Arabia is a prime example as it supports Sunni salafist fanatics in a global ‘outreach’ program to defeat the infidels of the world. The CIA created Chilean dictatorship of Pinochet (1973) destroyed a relatively egalitarian society and imposed the Washington consensus austerity on the country, at the cost of thousands killed and tens of thousands tortured. Neighbouring Argentina in 1976 suffered a similar CIA coup, with an estimated 30 000 “disappeared” thanks to CIA meddling. 
In the same era, Cuba assisted Angola and Namibia in gaining their independence while fighting the apartheid autocracy of South Africa, the latter supported by the U.S. Farther north, Cuba helped Ethiopia defeat the invading Somali army which again was supported by the U.S.
Obviously many of these wars had to do with the geopolitical anti-communist days, but it reflects the U.S.’ ongoing ambition to destroy anything even remotely independent of its desires, and more, to prevent a showcase for how anything slightly socialistic could be successful. Back to Cuba under embargo/sanctions: it is considered to be a ‘bad’ example of socialism because of its lack of ‘modernity’ – in other words lack of acceptance of the western corporate power agenda for global hegemony.
Castro’s foreign policy was obviously aligned against U.S. foreign policy. His domestic policies were the main point of antagonism. First off, he got rid of the corrupt mafia related government of Batista. Only later – when U.S. companies refused to be bought out at the artificially low prices they themselves had set (for tax purposes) – did he nationalize the companies. Even more egregious by U.S.standards was Castro’s distribution of land to hundreds of thousands of Cuban workers – not exactly a communist collectivist action, but one that defied the big landowners such as United Fruit (Chiquita – United Brands) whose employees were essentially indentured serfs.
For all its problems following the revolution, Castro had several large successes that seldom are viewed in western media. Cuba has one of the highest literacy rates in the world, more doctors per capita, and a lower infant mortality rate than the U.S. Life expectancy is slightly under that of the U.S., but can be accounted for as the embargo limits/prohibits medical supplies entering Cuba. It frequently is one of the first countries to offer medical aid to disaster stricken areas, recently notable being Haiti.
One of its larger successes has been with agriculture. Long supported with Soviet purchases of sugar and other agricultural products, this collapsed along with the Soviet collapse. Rather than succumb to western depredations, Castro allowed a limited free enterprise system for agricultural practices, creating what should be a model sustainable, healthy, environmentally friendly farm base.
Thus overall, Castro has had a positive impact on the world. He proved to be flexible yet resolute leader, he stood up to the power and greed of corporate America, he created a society – that while limited in its political expression – that is healthy and well educated. His steadfastness after the Soviet collapse created a sustainable agricultural base – and his long term survival allowed the U.S. to continue its illogical misinformed hubristic rhetoric against a country that in no way threatened the U.S. As demonstrated by U.S. policy/actions with China and Vietnam, none of its actions against Cuba make any sense at all, and are demonstrably regressive.
Castro’s legacy will live on generally as a positive force for the majority of the world. Thank you to Pierre Trudeau for keeping Canada open to Cuba (and China), and for Justin Trudeau for not copying the hate inspired rhetoric of our southern neighbours, or our own neocon U.S. sycophants.
 Perhaps a similar reaction as per Pol Pot in Laos – after western destruction of civil society, the influence of rabid anti-capitalist/western fanatics created their own domestic bloodbath. Now that I think of it, the same scenario is what created IS in Iraq and Syria.
 The list of U.S.-CIA interventions is a global phenomenon up to and including the neonazi supported coup in Ukraine and the recent destruction of Libya and Yemen as functioning societies. Previously Serbia was bombed into submission on the pretext of “human rights” shown to be a falsehood later, but allowing the U.S. to separate Kosovo from Serbia primarily to establish Camp Bondsteel, one of the largest military bases. Canada participated in all these destructive activities in support of the U.S. corporate/military interests.