Taeyeon - 2019: She had Four Seasons, All About You, and Spark, Four Seasons being her biggest hit to date, All About You being a big ost hit, and Spark doing decently
Mamamoo - 2016 or 2018: It's hard for me to decide which year, They had You're the Best and Decalcomanie in 2016, and Starry Night, Egotistic, and Wind Flower in 2018. YTB and Decal were both pretty big hits while Starry Night is arguably their biggest hit, Egotistic is a hit, and Wind Flower underperformed
Red Velvet - 2017: They had Rookie, Red Flavor, and Peekaboo, should be obvious RF is a national hit and Rookie and Peekaboo both are hits
SNSD - 2009: They had Gee and Genie, again obvious because Gee is a national hit and Genie did really well too
Apink - 2014: They had Mr. Chu and Luv, both of these were really big hits
BTOB - 2017: They had Movie and Missing You, Movie did decently and Missing You is a national hit