Xander Blake was the Leader of the Delta Squad of APF. There was not a single person in the APF who didn't know who Xander was.
He was an S-Rank Warlock. Even though he only led the Delta Squad, which was the weakest squad of the three APF Squads, there was no one who doubted his abilities. He was a respectful Warlock who was famously known even outside the APF.
Many influential people knew about him. As he was a member of the Delta Squad, he often dealt with Variant related problems of the general public, unlike the Higher Squads that placed most of their efforts on the Variant Uprising organization.
Because of this, Xander was known even by the general public. His reputation was very favorable in public.
Even though he wasn't on the list of the top ten strongest Warlocks in the country, he was still known to be a frightening Warlock. His flames were known to burn everything to cinders. It was also said to be hot enough to meld metals.