Possible unsporting situations I'm thinking about:

- When playing bullet games online (1 to 3 minutes per side), you move a single piece many times like `1. Nf3 ... 2. Ng1 ... 3. Nf3 ... 4. Ng1` etc. (to gain some time against your opponent)
- When you wait to lose by time instead of resigning (to avoid your opponent to play another game and to force him to keep thinking for nothing)
- When you wait the last minute you have on clock to force mate and win (to apply a psychological pressure to your opponent)
- When playing bullet games online, you promote all your pawns to queens to force mate with a big advantage (to apply a psychological pressure to your opponent)
- When you try to distract your opponent (to force him to make a bad move)

All these situations are legal in chess but can be considered as unsporting approaches.