What's The Work
Tangled: the Series is an animated series that follows the events of the movie Tangled.
Who is He/What Has He Done
Varian is the son of Quirin and a brilliant alchemist and inventor. In the series, he is a major character, who also served as a minor recurring character in Season 1, before turning evil as a result of Rapunzel's inability to save his father and becoming the antagonist of the second half of the season. In Season 3, he redeems himself and even becomes one of the main protagonists.
Throughout his heroic appearances, Varian has dedicated himself to helping/protecting his home kingdom of Corona, whether it be from the black/red rocks, giving his village hot running water, or attempting to defeat Cassandra and Zhan Tiri.
Of course, there's him turning evil and committing serious offenses against Corona, especially the royal family, towards the end of the first season (even if the circumstances beforehand make him an anti-villain), but I believe he fits the standard following his reformation.
Ever since then, any "malice" coming from Varian is essentially limited to occasional light-hearted mischief or snark. Nothing too much.
Though he does boast to Cassandra and lash out at Lance for disobeying him, these circumstances were very understandable, even if the former one was poorly thought-out. Otherwise, Varian isn't overly arrogant or temperamental, and seems to make an effort to prevent himself from being those.
Varian fits pleasant, being kind and caring to his friends and loved ones, as well as speaking politely even towards those who are hostile towards him for his past misdeeds.
He fits selfless, being willing to sacrifice his life to save Corona in the Season 3 premiere, and risking himself to stop Cassandra from obtaining the third incantation. He also faces his fear to rescue the people of Corona from Cassandra's red rocks.
Despite going more traumatic situations and being tempted by the red rocks, Varian doesn't give in to negative emotions such as fear or anger, and makes absolutely sure to stay on the right path, hence incorruptible. It seems impossible to imagine him willingly turning evil again.
Even after being drugged, injured, and kidnapped by Cassandra, he tries to make her see the error of her ways and help her, so I'd say forgiving. He also doesn't hold a grudge against Rapunzel for not checking on him after Zhan Tiri's blizzard.
Reluctant to kill, as while he does build an amber firearm to encase Cassandra in amber, he becomes very reluctant to use it, and only does it as a last resort, despite all the bad things she does to him. He doesn't even try to kill Zhan Tiri.
In spite of his young age, Varian stands out in terms of acts (including over Rapunzel, who is listed as Pure Good), given the aforementioned sacrifice, as well as stepping up to defend Corona despite being a commoner multiple times, something not even the main characters have done.
He also fits naive, not fully grasping the concept of magic, the rocks, or the Dark Kingdom, initially stepping up despite having no knowledge of things as a result of his father's secrets.
With all this in mind, I do think Varian is a qualifier for Pure Good. After all, a redeemed villain can still qualify if they end up meeting the criteria.