Avila escaped red for the lunge late on in a 3-1 defeat, but managed to then pick up a pair of stoppage time yellow cards for arguing with opponents.
The Argentine moved to Spain in 2017, initially on loan at Huesca, before joining Osasuna in 2019 where he received comparisons to the likes of countrymen Sergio Aguero and Carlos Tevez.
Tenacious, aggressive, gifted, and the wielder of a wicked right foot, Avila impressed with nine goals in his first six months at the club, and was on the brink of the national team.
However, his season ended when he ruptured his knee ligaments in January, and the injury then recurred at the start of the following campaign after a lengthy lay-off.
The 27-year-old's unfortunate injury history makes his tackle against Basque rivals Athletic all the more surprising, as he was just centimetres from inflicting a blow on his opponent, which could have resulted in similar injury.
Avila only entered the pitch in the 74th minute with his side two goals behind, and nearly cut the deficit with a superb strike brilliantly tipped onto the bar by Spain No.1 Unai Simon.
But, soon after, his moment of madness occurred.
Not only does history make the wild lunge such a surprise, but also the timing of the challenge, a minute into stoppage time with the game lost.
Williams was also outnumbered as he broke forward, with Avila's teammates in defence already in place, showing just how needless it was.
Williams instantly had the support of his brother Inaki, with the forward, previously linked with Manchester United, confronting the out of control Argentine who picked up his first yellow for the scuffle.
Still not cooled down from his lunge, Avila squared up to Athletic defender and Spanish international Inigo Martinez, putting his hands on his chest and neck, warranting a second yellow just minutes later.
The commentator described the horrendous move as 'disgusting' and 'horrible' with Avila likely to receive an extended ban when the incident is investigated further.
Elsewhere in LaLiga, the title race was re-opened by Real Madrid's 1-0 loss to Getafe, allowing second-placed Sevilla to close the gap to five points after beating Cadiz.