We saw what they did in the Americas (such as New Jersey, Delaware and PA, murders of Native Americans), their involvement in enslavement of Africans (Sweden had the gold coast), and the biggest one of them all, the oppression of Finland and its people. Finland was mistreated for most of its history.
They fought many a brutal war, and they repressed a peasant rebellion in the 1500's with a measure of brutality, but they also fostered the growth of agriculture, the arts and education in Finland.
Sweden also prevented Finland from being conquered by Russia on three occasions.
They also managed to prevent the Russian Novgorod and Muscovy from assimilating Finland prior to the formation of the Russian nation.
Sweden considered Finland part of the homeland, not a colonial province. The Finns were considered just as much a part of the empire as the Swedes themselves.
1637–1640 and 1648–1654 Count Per Brahe functioned as general governor of Finland. Many important reforms were made and many towns were founded. His period of administration is generally considered very beneficial to the development of Finland.
1640 Finland's first university, the Academy of Åbo, was founded in Turku at the proposal of Count Per Brahe by Queen Christina of Sweden.
1642 The whole Bible was published in Finnish.
Really, aside from the little ice-age, Finland had a strong economic system and produced tons of goods, such as fish and tar, for mainland Europe. The wealth primarily stayed in Finnish hands, as well.
It wasn't until the Russian invasions in the 17th century, when the brutality occurred and the tragic loss of Finnish heritage occurred.
The Great Northern War (1700–1721) was devastating, as Sweden and Russia fought for control of the Baltic. Harsh conditions—worsening poverty and repeated crop failures—among peasants undermined support for the war, leading to Sweden's defeat. Finland was a battleground as both armies ravaged the countryside, leading to famine, epidemics, social disruption and the loss of nearly half the population. By 1721 only 250,000 remained.
Russia occupied Finland multiple times in the 17 and 18oo's, finally conquering the Finns in the late 19th century.
So, no Sweden wasn't particularly brutal, compared to England, Spain and France.