I tried to find this on my own but couldn’t find anything.
Has any 4 star character ever been featured (boosted) outside their introductory event?
For their first PvE after they come out and their own PvP are the only two times. Well, unless you count the PvP where everyone becomes 270, so as long as you had a maxed covered 4* even if they were level 100 they would get buffed to 270, outside that, no.
I haven’t seen them boosted outside of the introductory event and specialty events, such as Earth’s Mightiest or the recent Divine Champions.
Before he was reworked, there were a few Wolverine PVP’s where the 4* 3* and 2* each were boosted and had their own node. It’s was terrible for retaliations though as they rotated nodes even though you could only use one particular wolverine for each node