I think their treatment of Jin is solid. The wider cast do treat him as a saviour - which makes sense to some degree, even if his actions in 6 are tough to swallow. But at least Jin is self-aware of his past throughout and genuinely doesn't feel like he deserves to live. He says, on multiple occasions, he's happy to die to finish things once and for all. His actions aren't swept under the rug - though I can understand why some would say they aren't directly tackled in a satisfying way. Whether you think he deserves the ending he got or not, I think they do a good job bringing him back as a character after doing their best to ruin him in recent instalments.
It's a bit muddled, but I think they stick the landing for Jin, even if awkwardly.
Reina is brilliant. I said it a few pages back but - she's a sinister schemer who masquerades as the group cheerleader. From her overexuberant interactions with Jin and the wider cast, to her more calculated inner monologue, she's someone you can't take your eyes off. When she head-butted Devil Kazuya and gave him a smirk, I thought yep, this is the good stuff. Great design, great voice work and used perfectly - she's always around, has some badass moments but never overpowers the main story.
The idea of her having the devil gene and the questions that poses are cool, but I do think it took away from the ending a bit. Jin finally succeeding in destroying the devil gene was really powerful and opened the doorway to a new era of Tekken. He'd been trying to do it for decades. Kill Kaz off, let Jin live a quiet life with his girlfriend and move the franchise forward. As it stands, it's presumably Jin and Kaz squaring off against a devil Reina soon… it's not bad. I just think this was their chance to massively shake things up.
In some ways, they could have had Reina help Jin defeat Kazuya, allowing Jin to ride off into the sunset and promoting Reina to series protagonist. But I do like sinister Reina so…
I've not played the post story unlockables, but Jun's return feels like a big missed opportunity and I felt like her involvement could have been expanded upon.
Overall the pacing and construction of the story was a lot better than 7. The story dialogue is campy and utilitarian in equal measure, but it's churned through quickly enough that nothing overstays its welcome. Good fun, just wished they made some bolder decisions for the future. So many cool callbacks too. If you're a big Jin fan - like me - you can't not love the last 10% of the campaign. Angel Jin, T3 Jin, Kazama-style Jin…
… whatever you say about it all, a major part of the story was Jin accepting all aspects of himself, so to see that actually play out in gameplay is wicked - and something even more accomplished story games get wrong all the time.