Warning: contains spoilers for Dragon Ball Super chapter 59!
Dragon Ball Z: Lord Slug is notorious among fans for being one of the franchise's worst movies, but Dragon Ball Super has already taken inspiration from the film's proprietary transformative state to create yet another stage of Ultra Instinct that's explored during Dragon Ball Super's Galactic Patrol Prisoner Saga. Even the wish that the titular villain makes on the Dragon Balls in Lord Slug mirrors what the Planet-Eater Moro wants in the manga.
In the Lord Slug movie, the titular Namekian comes to Earth with the intent of conquering the planet. The Z Fighters rush to the scene but are no match for his minions as Goku, in an unsurprising turn, is currently indisposed. But when Goku finally arrives, he soon finds himself overpowered by Lord Slug, getting axe-handled to the ground, thrown into objects and pummeled mercilessly. Goku is only able to put a stop to Slug's onslaught when he suddenly undergoes a transformation that isn't quite Super Saiyan.
The Saiyan is surrounded by golden aura that causes his hair to stand on end and gain a reddish tint as opposed to a full-on golden hue, while his pupils disappear entirely rather than turning greenish-blue. Called a Pseudo Super Saiyan, Goku is able to amass incredible power; a strength that steadily increases as he continues to yell nonstop throughout his short time in this heightened state. But despite its power, Pseudo Super Saiyan cannot reach anywhere close to what Super Saiyan can achieve. It is also quite unstable, as Goku's aura quickly deteriorates once Lord Slug snaps Goku out of his trance-like state.
In Dragon Ball Super, Ultra Instinct is the "absolute peak" in martial arts mastery, as the user is able to let go and allow the body to move on its own rather than the user controlling its movements through thought. For Goku, achieving the true form of Ultra Instinct leads to the Saiyan unlocking a transformation that transcends Super Saiyan Blue. However, like how Super Saiyan has a Psuedo Super Saiyan state, so too does Ultra Instinct: Ultra Instinct -Sign-.
Like Pseudo Super Saiyan, Ultra Instinct -Sign- is more unstable and not as potent as the true form. Goku first reaches this state when Jiren almost kills him during the Universe saga, but he isn't able to activate it willingly. The Saiyan is later able to summon -Sign- voluntarily for his fight against Moro, and uses it to avoid the Planet-Eater absorbing his chi, as revealed in chapter 59. Similar to how Pseudo Super Saiyan doesn't turn Goku's hair completely gold, Goku's hair is only partially silver in -Sign- as opposed to how it becomes almost completely white when he achieves the true Ultra Instinct.
But a limited transformation isn't all that the Galactic Patrol Prisoner Saga borrows from Lord Slug. After gathering the Dragon Balls on New Namek, Morrow wishes to restore his magic power to how it was millions of years ago, before the Lord of Lords sealed it. This is quite similar to what Lord Slug wants. The Namekian is originally decrepit like Moro was at the start of Dragon Ball Super and wishes for eternal youth from Earth's Dragon Balls, restoring his strength to when he was at his most powerful.
Regardless of how fans feel about Dragon Ball Super, it's intriguing that the series that revitalized the franchise with a revamped continuity is taking inspiration from a Dragon Ball Z movie that most fans consider one of Dragon Ball's lowest moments. But from among the wreckage that was Dragon Ball Z: Lord Slug, Dragon Ball Super is able to salvage the few standout aspects and use them to improve the ongoing story of Goku and his friends.