If you had to make a level 17 character using only PHB/Wildemount races and classes with other restrictions/benefits, what would it be?

My Sunday game has recently swapped over to an old campaign that several of the players were playing in before I found this group, and they're all level 17. I've played a stupendous amount of DND at this point and am stumpted on how to make a not cannon-fodder fun character for this campaign with these restrictions/ benefits. This is not a roleplay group either so fun has to be derived from combat. Some of the stuff for CC in this campaign is crazy strong but I don't wanna just blow it up and be crazy OP.

Race and Class from PHB only, Items and spells can be from any official source, but can't step on other party members toes so Warlock, Rogue, and Cleric are out. The warlock polymorphs into a dragon every fight, the cleric is a Tempest one so lighting max damage go brrr, and the rogue is initiative specced out to get crazy damage on the first turn of combat every time.

Now admittedly I get some AWESOME benefits to joining this late, also the previous restrictions of PHB also fly away and can be from any official source. There's a free starting feat, and you GET A FEAT along with every ASI, so mindblowing. I get a legendary magic item, also a rare, 4 uncommons, and 8 commons. Like there's no doubt I can make something ridiculously powerful but I'm less interested in that than something like comboed things to do niche stuff.