In some questions (see this one, for instance) it is reported that, according to what was stated in the books and proved in the TV show, wights and white walkers can be killed using a weapon that was forged with dragon fire:
- fire itself (for wights)
- Valyrian steel
Fire and obsidian was proven effective against wights in the last episode of season 7, where
Jon Snow confirmed that the wight brought to Cersei could be killed "by fire" or "with dragonglass"
However, due to the events happening in Season 7,
Viserion was killed and brought back by the Night King.
Does dragonglass or fire work in this situation too? I ask this because
Viserion (a wight) is actually a dragon, it can produce fire itself (probably, as discussed in this question), and it is said that obsidian is either created by dragons or by fire in the Earth (source)