It's powerful stuff, isn't it? Methadone is often overlooked in CTB discussions because it has a very unique profile. It's a long acting full opioid agonist, meaning its effects come on slower but last far longer than drugs like heroin or oxycodone. That delayed onset is why some people accidentally take too much, thinking it hasn't kicked in yet which can lead to unexpected overdose several hours later. But the euphoric clarity it brings? That's part of why it's so used in opioid programmes too.
From a CTB perspective, the appeal is minimal panic, less violence, and the sense of being mentally present even as the body begins to shut down. It also doesn't trigger the same intense nausea or respiratory panic that some fast acting methods do. That said, if someone were seriously planning with it, tolerance, dosage, and timing are key, especially since methadone builds up slowly, and death can be delayed for hours. It's also often reversible with naloxone if you're found so that has to be factored in too.
If you're going to explore more with it, take care because it's potent, unpredictable at high doses, and easy to misjudge without opioid tolerance. There is actually a video I've seen of a man dying to this over discord call and whilst it is really sad (mainly because of the fuckwits he was live on discord to as he did it laughing at him, paired with his parents finding him three days later), it made me wish I had access to it.