Five people have been arrested after an attack on Asda workers in Clapham.
GMB Union has condemned the attacks, saying such incidents are on the rise and parliament must act now to toughen the law.
A video posted on social media on Thursday showed a man in a Spider-Man costume attacking numerous Asda employees, including a woman, who he kicked in the throat and punched in the face.
The woman fell to the ground.
A person in a wheelchair is seen to be pulled back from the fight, and the man in the Spider-Man costume can be seen hitting people with what appears to be a single crutch.
Metropolitan Police officers were called to reports of a disturbance at the supermarket on Lavender Hill near Clapham Junction at 10.40pm on Thursday, they said.
Two men aged 37 and 35, and an 18-year-old woman and 17-year-old girl have been arrested on suspicion of affray and violent disorder, and 31-year-old man was arrested on suspicion of actual bodily harm, grievous bodily harm, affray and violent disorder.
London Ambulance Service also attended the scene, treating five people and taking one 20-year-old woman to hospital with a minor injury.
Another clip shows a brawl in the warehouse area of the shop involving Asda employees and several people wearing costumes.
An Asda spokesperson said: “We are aware of an incident which occurred at our Clapham Junction store late last night.
“We do not tolerate any form of violence or abuse towards colleagues or customers and we are working closely with the police in their inquiries.”
GMB condemned the “horrific attacks,” in which some of its members were involved.
Mark Wilkinson, GMB Senior Organiser said: “GMB cannot condemn strongly enough the actions of these people and we thank the police for their swift action in arriving to help protect our members from further harm.
“The video footage is absolutely horrifying and we are offering whatever support is necessary to any member who were affected during the incident.
“We take the health and safety of our members very seriously and will be working with store management to establish how this was allowed to happen and to ensure that safeguards are in place to prevent recurrence.
“Sadly, GMB is all too aware that whilst Clapham Junction is an extreme example, attacks on retail workers are on the increase. Parliament needs to act now to toughen the law.
“If you were affected in any way by the incident, please contact GMB straight away and we will ensure you get the support you need.”
Anyone with information about the incident is asked to call police on 101 or tweet MetCC quoting CAD 7883/22Jul.
Additional reporting by Press Association