I was thinking earlier how one of my favorite custom digimon lines goes Data -> Virus -> Vaccine (Red Otamamon -> Yo!Yo!mon -> Shootmon), but I was wondering to myself if we've ever seen any digimon not owned by a player character ever switch attributes at every stage?
Of course your partner in a v-pet, Story, or World game can but have we ever had a scripted character's partner or a wild digimon change attributes every time it evolved?
The closest I can think of off the top of my head is either leomon, since his only 2 on screen stages are vaccine and data, or biyomon from saviors since it briefly switches to data before becoming vaccine again.
Aquilamon is a Free. It still changes it up, but it's not Data outside maybe a trading card or something since the o.g. card game didn't use Free.
looking through every tamer ever, there's no one who has their attribute change three times whilst having a full line best we have for 4 guys (rookie to mega) is Maki and Kazu
But Takuma's Agumon can go
Free - Vaccine - Virus - Data - Vaccine - NO DATA, so he wins
Chitose has a Syakomon that goes into Seadramon then Whamon but no Mega. So Virus to Data to Vaccine. Give him Vikemon as a Mega and he can have all different
The popular go to Impmon line has Virus - Data - Free - Virus though the one for Ai/Mako has Data lv5 not Free lv5
The issue is having three main attributes meaning you need Free in there somewhere
Also just realised I misunderstood the question, so that Impmon default line does change three times. Changing to Data, then Free, then back to Virus.