Social evils could be generally summed up as relating to anything that could be harmful to society or the community at large.
An example of this could be crime, alcoholism, abuse, or racism which are all problematic issues that can cause harm to the society at large.
One of the most predominant social evils of our time is organised crime. There are many impacts of crime on the wider community as it often goes hand in hand with violent behaviour. Violence can inevitably cause extreme harm to individuals which is why crime is associated with being a most notable social evil.
Addictive drivers such as alcohol and gambling are also renowned as being a social evil that have impacted the world at large.
Excessive alcoholics often have problems with relationships, abuse and physical or mental violence. Gambling has seen many individuals being left quite heavily in debt and is the cause of financial breakdown for many families who have one or more people who gamble excessively.
Another significant social evil is racism and religious intolerance.
Racism has divided communities, speared hate crime and destructed unity within society. Religious intolerance has made people less able to practice their faith without being ridiculed.
There are many social evils that are, unfortunately, still prevalent in the world today - but in time and with the right attitude these issues can hopefully be overcome.
I hope this answers your question :)