1.Evil Shenlong killed Piccolo as revenge for their last meeting.
2.Piccolo killed Brolly for harming Majin Brolly.
3.Piccende, the fused piccolo and Dende, killed Babidi
4.Android 17 and Krillin died when android 17 used a sicuide blast
5.Goku killed shenlong for killing piccolo