Note: There may be unmarked spoilers for his Nuzlockes ahead, so beware.
The end of the battle against Champion Wallace in the Emerald Nuzlocke
Since this battle has been known for a very infamous incident against Wallace's final Pokémon, his Gyarados, this is where the whole thing needs to be explained and addressed. Before beginning, though, he disabled comments, where some things were partly mentioned, so I can't accurately get to everything. But i'll speak this to the best of my ability.
First off, he didn't send in Taquito right away because Gyarados was more than likely faster and he thought it Earthquake (which he did in fact mention in the comments before he disabled them). That goes against what happens later. Anyway, he opens with Quinoa the Walrein, and Gyarados is faster and uses Dragon Dance, while Devin gets in Encore, now it's locked into that. Then he utilizes Toxic as Gyarados' stats continue to boost. Now the logical choice would be send in Taquito the Magneton and murder that thing with Thunderbolt. But he then goes in for Frittata, and after two more boosts from the opposition he uses Confuse Ray.
Now he has Gyarados with +4 Attack and Speed, but also confused, right? He uses Fly, and Gyarados does in fact hurt itself for big damage before that. However, Gyarados lives with a sliver of health from poison damage, which causes Wallace to use a Full Restore. Now, another big mistake was using Fly instead of going straight for the attack. If he had used Sludge Bomb, it would have been game over for sure, because even if it weren't for the confusion damage, Sludge Bomb would have most likely knocked it down to the point where it would have succumbed, because when Wallace's Ludicolo was out, Sludge Bomb almost killed it in one hit. True, Gyarados does have a little more HP and Defense than Ludicolo, but given his condition at the time he probably could have made it down to the punch. Because Encore was still in effect, he wouldn't have had to worry about being attacked.
After Gyarados' encore ended, he mentioned that he didn't know what other moves Gyarados had aside from Dragon Dance and Hyper Beam. So he did try to use Confuse Ray again, but he was beaten to the punch with Hyper Beam.
Now is when we're really at the frustrating part. He sends in Taquito, and you'd think that because Gyarados has to recharge, it's game over, right? Instead he uses Thunder Wave, then suggests he has a plan and uses Reflect. But then, Gyarados uses Earthquake. His reaction here implies that he probably didn't know it had it. But that goes against why he didn't send Taquito in against Gyarados in the first place. Was he planning to use Thunderbolt after setting up Reflect? Or did he have no intention to use Thunderbolt at all and plan to switch out after that? He does win though, by bringing in Spaghetti, and Devin's Hyper Beam barely fails to KO it, but Wallace then misses with it, and Marriland does in fact win.
So now we get to Part 56, The Fanart Special, where before releasing Frittata and Taquito, he gives us what he has to say for himself. To start with, his main concern after using Encore with Quinoa was being mindful of if Encore was going to wear off or not. Now that is understandable, because one, earlier in the battle one of Wallace's Pokémon (I think it was Milotic) had Encore last three turns or something, and prior to Platinum it can last 2-6 turns (in Platinum and HGSS it lasts 3-7 turns, and in Gen V it always lasts three turns). But regardless of what he did, there was a chance something was going to die if Encore had lasted the minimum of two turns, because had that happened whoever was out most likely would have died to a Hyper Beam (or in Taquito's case, Earthquake). So when he had used Toxic, if Encore had ended there, he would have had pretty much no choice but to sacrifice someone (although all things considered, Taquito probably could have survived a +2 Hyper Beam since it was resisted).
Then, he apparently used Reflect in anticipation of Earthquake. However, that's probably a moot point. Did he really think he was going to survive a +4 Earthquake, even with Reflect up? If he did anticipate Earthquake (which, again, his reaction implies he didn't), he could have brought in Spaghetti to negate that.
So for the people that (nearly) rage quit his videos after that battle, or anything along those lines, this is the insight I have to offer. And he's had some other moments his fans aren't really proud of, but that's just how it goes.