You are introduced at the start of the final battle to much cheering with the comment that this would be your first tournament win ever.  Colress is introduced as well, with the comment that he wishes to 'bring out the power of pokemon'.  There's a lot of cheering for him as well as he moves up to the platform.

As the giant screen displays the matchup, Colress explains that, as he is a researcher, he's trying to find the ideal way that 'things should be'.  He wants to know how to bring out the greatest strength in pokemon, and says he hopes for it to be the trust between pokemon and trainer, 'just as it has always been'.  He even goes on to say he hopes you will teach him that this is the truth.

Battle: Colress
Opponent: Magneton Lv 25, Elgyem Lv 25, Klink Lv 25

While Colress is really fond of paralysis and other, more obscure status effects (Heal Block on his Elgyem, for instance), he is still battling at level 25 and even Steel typing should have a hard time overcoming your advantage here.  Fire attacks are a very good way to go, and if you have a Growlithe with Snarl on it, or even just a Pignite, that will put a huge dent in pretty much everything he's fielding.  It’s a bit curious to note that only his Magneton is evolved- why this is the case, particularly when Cheren has an underleveled Stoutland, is unclear.  Nothing he’s said indicates that he would try to avoid evolving the pokemon he trains, after all.

It is to be fully expected that you have won all three battles and thus the Driftveil Tournament.  With all the training you’ve done and having to overcome Clay besides, it’s very likely that your team is over level 30 already, making you more than a match for the level 25 opposition.

With the final battle over, you are declared the winner- to much cheering and launching of streamers and confetti.  Colress is unsurprised and very complimentary, telling you that he expected this and he's sure your pokemon are very happy to be with you.  According to him, you bring out the best of what they have.

Thus concludes the Driftveil Tournament, and you recieve 1 BP as a reward.