IZARIANS

The Izarians are an humanoid species that developed a technologically advanced civilisation on a planet orbiting the star Izar.
They have developed teleporters on an interplanetary scale and advanced bioengineering and cybernetics which allow them to create large artificial beings and to modify themselves. High ranking officials will usually have undergone extensive modifications, often giving them giant proportions and non-standard physical features.
They came to Earth some 200 000 years ago with prospect of invasion but halted their plans upon discovering the planet atmosphere was not fully compatible with their biology. Their scouting party nevertheless stayed on Earth and established a secret base at the bottom of the Pacific ocean.
Toward the end of the 20th century, they realised that their homeworld was doomed as another planetoid was on a collision course with it. They reestablished plans of Earth conquest but were defeated.
Source: MagneRobo Gakeen TV series

MAKUU / C-REX

Makuu aka C-Rex are an aggressive and expansionnist advanced species naively bent on universal domination under the domination of Don Hora/Don Horror/Lou IBMX-11, a monstrous six-armed idol-like being which lives in a large structure in a pocket universe. It remains unclear if this dimension is a crossroad between our universe and another one and if the Makyy actually come from it but Don Hora is able to conjure other temporary pocket dimensions to serve as arenas where his subordinates terminate his adversaries.

The bulk of the Makuu/C-Rex forces are composed of humanoids with vaguely reptilian features. the most advanced can assume human form and even transform into bulkier monstrous creatures. Given the diversity of monstrous form different specimen can adopt, it is most likely the result of manipulation of the individual, either chemical, genetical or else.
The Makuu/C-Rex were exterminated from this universe around the end of the 20th century.
Source: Space Sheriff Gavan / X-Or TV series

KALONIANS

Advanced Humanoid species with cut-steel-blue pigmentation from the planet Kalonia in the Wolf-Lundmark-Melotte Galaxy. They were pawns of the Eddorians.
Source: E.E. "Doc" Smith

CHICKLADORIANS

Advanced species of pink skinned humanoid with triangular eyes which evolved on the planet Chickladoria.
Source: E.E."Doc" Smith

VELANTIANS

Velantians are part of the Arisians Breeding program that developed on Velantia III They are an advanced reptilian species that developed space travel. Dragonlike, they are massive, winged and possess 2 pairs of eyes.
Source: E.E "Doc" Smith, David Kyle, Lensmen from Rigel

RIGELLIANS

Rigellians are part of the Arisians Breeding program that developed on the superhot, high-gravity world of Rigel IV. They are an advenced species that developed space travel. Monolithic, they are quadruped with an egg shaped body with four prehensile tentacles coming out the their middle and four mouth near their top.
Source: E.E "Doc" Smith, David Kyle, Lensmen from Rigel

EDDORIANS

The Eddorians are a psychic dictatorial, power-hungry shapeless species from the planet Eddore in another universe where the laws of physics are different. They were attracted to this universe by the observation that the Milky Way and a sister galaxy, the Wolf-Lundmark-Melotte galaxy might be passing through each other. The Eddorians believed that this would result in the formation of billions of planets and the development of life upon them. Dominance over these life forms seemed to the Eddorians the logical course of action. This dominance isexercised on their behalf by a hierarchy of underling races. The Eddorians themselves are physically similar to various lower Earthly life-forms, reproducing by fission but by a process more similar to budding than to cell division, except that each being's memories are preserved. They are highly competitive, extremely long-lived, and almost impossible to kill

Source: E.E. "Doc" Smith, Triplanetary

ARISIANS

Peaceful humanoid species that have developed what could be among the first sentient civilisation in our universe. They have forgone physical and developed tremendous mental power. Foreseeing the invasion of our universe by the Eddorians, a species from another universe, they began, over 2 billion years ago, a covert breeding program on every world that can produce intelligent life, with the aim of producing a means to eventually destroy the Eddorian race. Their work done, their plans are to remove themselves from the universe.
Source: E.E. "Doc" Smith, Triplanetary

ANDREENIDS / ANDRINOS

The Andreenids are an insectoid species indigenous to planet Eternia. Their body is roughly that of a winged humanoid. Although individuals have their own personnality, they follow a hive social structure. Distrustful and proud, they keep their contacts with other species minimal. They are not known to use any advanced technology.
Source: He-Man and the Masters of the Universe.