(Source: Wikipedia, with edits by Espionne)
The L.A.M.O.S. (League Aiming to Menace and Overthrow Spies) are a group composed of the recurring villains in Totally Spies!, including Terrence Lewis, Tim Scam, Myrna Beesbottom, Helga von Guggen, and Boogie Gus.
Terrence Lewis ("Terry") is Jerry's evil twin brother and the primary arch-nemesis of the spies. In the Season 3 finale "Evil Promotion Much?", the spies were selected for promotion to the next level due to their stunning success, and were sent to Terrence for the training required to become Super Spies. At first, Terrence appeared to be an easy-going, relaxed administrator, but later turned against the spies and forced them to try to eliminate Jerry. His motive was that when he and Jerry were in school, they helped each other cheat by copying the answers off each other during an important exam, but when the teacher found out, Jerry cowardly blamed Terrence, leading his brother to be expelled from school. Terrence explained this incident as his primary reason for modifying his face and voice through plastic surgery to look different from his twin, saying that he would "hate to look like [his] "evil" twin". He wears a white curly wig and runs the L.A.M.O.S. from a leaky sub underwater.
Tim Scam is the most recurring villain who appeared in six episodes. He is a former WOOHP weapons technician who was fired for illegal use of WOOHP technology, and attempts to get revenge on the organization. Scam first appeared in the show's second episode "The New Jerry", in which he kidnapped Jerry and replaced him to use WOOHP for his plot. Sam also developed a strong crush on him before she discovered he was evil. In "Mommies Dearest" he attempted to get revenge on the girls by brainwashing their mothers into killing their daughters. In "Morphing is sooo 1987" Tim attempted to destroy WOOHP using liquid-metal robots capable of mimicking the appearance of others. He reappeared in season 4 and became a member of the L.A.M.O.S.
Tim Scam is highly intelligent. He originally developed a heat-ray capable of evaporating the Earth's oceans while working for WOOHP. He will likely remain a persistent nuisance to Jerry and the spies.
Unlike the show's other villains, who are usually "themed" bad guys whose personalities typically center around a single bizarre personality disorder or childhood trauma, Scam comes across as completely sane (albeit sociopathic). Also, unlike the other villains, whose plans generally involve indulging in their twisted obsessions (which often involve brainwashing people), Scam's plans are centered around all-evil deeds to accomplish his malevolent objectives. Scam kills for killing's sake.
Myrna Beesbottom is a former WOOHP agent. Her first appearance was when she was still good and became the girls' nanny in the Season 3 episode "Space Much?". Her next appearance (her first appearance as a villain) was in "Evil Valentine's Day Much?" where she tried to marry Jerry so she could take over WOOHP. She has made a couple of Season 4 appearances and her lead role was in "The Dream Teens" when she created plasma robots to become the spies' boyfriends, before draining their energy in order to eliminate Jerry and WOOHP. She has recently been arrested and is temporarily apart from the rest of the L.A.M.O.S. Despite her obese build Myrna is extremely agile and strong, and it's also hinted she specialized in ninja training.
Helga Von Guggen
Helga Von Guggen is a rogue fashion designer and one of the show's regular villains. In her first appearances on the show, she had a bodyguard, Trode, who did her bidding.
In "Wild Style", Trode met the spies while they were investigating the mysterious disappearance of a cruise ship, along with its crew and passengers. Unbeknownst to them, Helga was the mastermind behind the abductions, and instructed Trode to infect one of the spies with her mutation serum through the use of a dart, resulting in Clover being mutated into a catgirl. At Helga's hideout, Helga revealed to the spies that she was using the serum to turn humans into animal-like creatures in order to produce instant-fitting fur coats. Ultimately, Helga fell victim to her own mutation serum and transformed into a massive Chimaera-like mutant monster. She was defeated and captured by the girls.
In "Fashion Faux Pas", Helga returned with a scheme to use a fashion clothing line to strangle people to death. At her hideout, she told the spies her plan, and ordered Trode to keep an eye on them. In the end, she was turned in and captured again. It is never explained how she returned to normal in this episode, though it can be assumed she used the reverse serum that cured Clover and the other victims of the mutation.
She later appeared again in Season 4 as a member of the L.A.M.O.S., having been disposed of Trode, whom she deemed to be incompetent (he might have been written off). In "Evil Jerry" Helga was arrested, but she returned again (presumably having escaped) in "Like, Sooo Totally Not Spies", and at the end of the episode she, as well as the rest of the L.A.M.O.S., were arrested.
Boogie Gus is a black 70's-loving villain and a former WOOHP janitor who first appeared in season 3, "Forward To The Past'". He planned to go back in time and convince Jerry to create an evil WOOHP with him, which would stand for "World Organization Of Harming People". In Season 4, he joined the L.A.M.O.S. and became an 80's lover, even though he still sported his 70's afro/disco hairstyle. In "I Hate the Eighties", he planned to turn the world into his own 80's wonderland and to make Jerry and the spies younger, to the extent where they would not be able to stop him. In "Like, So Totally Not Spies", it was implied that he is bad at keeping secrets, much to Terrence's and Helga's annoyance.