It has been VERY weak.
2018 - All of the top ggs came back
2017 - Wanna One, Sunmi, Blackpink, Apink, RV
2016 - BTS, Sistar, Apink
2015 - Sistar, SNSD, Shinee, Apink
The best thing we've gotten for a summer comeback was Icy and even though I like it, it's not it. Imo SM needs to get their shit...