is it possible that he was misrepresented to malign the Soviet Union

"Maligning the Soviet Union" certainly wouldn't explain why Khrushschev denounced his killings in his "Secret Speech", which was delivered at the 20th Party Congress in 1956 - it was not a public speech and its intended audience was specifically Communist party members. Khrushschev notes that, among other things, 70 percent of the 17th Party Congress (of 1934) was shot, and that Stalin conducted "mass terror" (Khrushshev's words) on the party and other sectors of the Soviet population. He further notes that this repression used mass arrests, forced confessions and execution to silence anyone that Stalin considered a threat, whether real or imagined.

Now, of course Khrushchev had his own motives for detailing these acts - he was part of Stalin's inner circle, but was trying to distance himself from the old regime after Stalin's death. But by the same token, considering that Khrushchev was speaking to a thoroughly communist audience, he also focused specifically on areas, such as the cult of personality and the persecution of communist party members, where Khrushchev felt Stalin had deviated from Marxist-Leninist norms (so topics like forced deportations and the famines weren't touched at all).

Anyway, the opening of the Soviet archives from the Gorbachev era on has provided documentary proof on aspects of Stalin's involvement in the Soviet repressive machine. He personally signed tens of thousands of death warrants, often a few hundred at a time. Admittedly the vast number of death sentences in the 1930s Purges (and some 800,000 were executed, per the archives) were not signed by him, but were conducted by lower level party officials after being given execution "quotas" by the central government. There is academic debate as to how much of the purges were driven by lower echelons of the party and state, and how much was directed by the center (this roughly parallels the "functionalism" vs. "intentionalism" debate over Nazi Germany and the Holocaust), but there is documentary proof that Stalin was aware of and approved a big section of the purges.

The Soviet archival records also bear witness to the large numbers of Soviet citizens who were persecuted but not outright executed in the purges. The records for the gulag system alone show some three million people imprisoned over the period from Stalin's rise in the late 1920s until World War II in extremely harsh conditions. Even when many of these people were imprisoned for ostensibly non-political crimes, they were often crimes that had extremely draconian punishments - the infamous "Law of the Spikelets" gave a punishment of up to 10 years imprisonment for stealing a handful of grain, and Stalin's government approved the reintroduction of the death penalty and the eventual lowering of its application to children 12 and over. The rationale for laws such as this were effectively to institute a "tough on crime" policy, which to some extent explains a large part of Stalin's popularity even today, but these were extremely harsh punishments that were not meted out with some sort of impartial justice.

In terms of other questions around possible genocides (in mass deportations and famines) I'll point you to this older answer I wrote here. My short summary - there is debate among serious historians of the Soviet period as to how intentional the mass deaths in these events were, but even the historians who consider most of these deaths to be unintentional note that official government callousness to large losses of life played a major role in causing these events, and Stalin himself repeatedly showed himself to be more callous that even other members of his regime.

Also I will note that while extremely high death counts like "Stalin killed 60 million people" are pretty much bunk, current historians consider the death toll caused by Stalin directly or indirectly to be in the vicinity of 9 million. So he definitely is responsible for millions of deaths.

As far as current numbers: in Russia at least, in various polls something like close to half of the population reports a fairly positive opinion of Stalin, about a quarter a sharply negative opinion, and the rest are neutral. Which is to say that he is a controversial subject that people have mixed and strong emotions over.

The 20 year rule prevents me from getting too far into the reasons for this in the 21st century, but at least through the 1990s there was a feeling that Stalin, despite his mass killings, at least was tough on crime, enforced some sort of social egalitarianism, and made the USSR a superpower - these would have been acutely felt by segments of the population, especially older ones, who saw Russia in that period shrink from the world stage, see a sharp rise in poverty and inequality, and a massive explosion of violent crime. But anyone who thought that all of Stalin's misdeeds were fabricated would be willingly ignorant (which given how history was taught in the Soviet period could be very possible), not only to the personal histories around them (stories of deportation, dekulakization, imprisonment and worse), but also to the personal words of Khrushschev, Gorbachev, the samizdat writings of authors such as Solzhenitsyn, or the painstaking work of groups such as Memorial, one of the first non-party organizations to be legalized in the USSR, which has maintained lists and a database of all victims of Stalinist repression (you can visit their website here, they even have scans of the mass death sentences signed by Stalin).