the only drugs that will almost invariably cause at least a little bit of damage are coke/amphet and their deriatives ie the accelerants, and high levels of alcohol
Actually, in terms of long-term, irreversible damage, the worst drugs are ecstasy and methamphetamine. Both kill really key dopamine channels, fry seratonin reuptake and release mechanisms, and in general reconfigure things about your brain chemistry that can't be reversed. Ecstasy at any dose is a neurotoxin, which means even a tenth of a "dose" is poisonous. Because it isn't usually a "drug of abuse" with a high risk of psychological dependency most people don't use it enough to incapacitate themselves. They still haven't figured out how bad its very long-term effects are. Meth permanently damages long-term memory and is seriously addictive. I'm sure its memory-obliterating effects are the reason why some people like it, though. I think withdrawal symptoms from meth are the most potentially lethal of all physically addictive drugs and include stroke seizure. In the U.S., cleaner and more efficient amphetamines are prescribed in pill form for ADD/ADHD maintenance treatment.
Coke is a stimulant--it will change your brain chemistry and definitely affect mood for longer than its high lasts, but its effects are temporary. Some people experience "cocaine psychosis" under its influence which can get pretty extreme (Naomi Campbell). The physical dependency is nowhere near as hard to overcome as the psychological addiction, but its physically damaging effects are not nearly as bad or as long term as amphetamines. Does dry out your skin and will make you look old if you insist on losing enough sleep. In the U.S., doctors also use cocaine-like stimulants (Ritalin) for ADHD/ADD in teens and preteens.
There are lots of pharmaceuticals that are insanely damaging, not to mention over the counter drugs that are bad for you in ways that would make people sue the manufacturers for if they were only told. They just don't tell you about them because the good guys (mostly white men) make money from those drugs instead of Columbians and other non-whites.
In terms of drug use being a sure-fire way to shave off those last terrible years--you could wear down your systems and organs and die younger, or you might just make your nursing home stay much much more torturous and expensive. Marijuana use has been linked to a decreased risk in Alzheimer's, which is another reason why it's stupid THC isn't used medicinally in the West as a general practice.
Drug use is worth incurred damage in my opinion if your experiences seem worthwhile or add something interesting and productive to your life. If they don't, or if they're a destructive force, you're wasting time and it wouldn't be worth future damage just to live out some rock and roll ideal (cliche). Sadly, I think drug use is the closest thing people have under capitalism to forging experiences outside of the "entertainment" modes clean and sober people use. Which is not to say that it absolves you from capitalism, but it's the only way I can think of to intellectually resist, say, the things TV tells me to want and like and do in any literal experiential way. It's a distraction, too, but at least its content is directed by me rather than advertisers who want to appeal to Texans who like Fox News.
Before drug use was pathologized barely a century ago, drugs (especially hallucinogens) were openly used across most cultures to perform rituals (to spiritual ends) and rites (to social ends) and addiction was unheard of. Science took these drugs and created exponentially stronger forms that are still essential to basic medical practices like surgery (benzocaine, lidocaine, topical anaesthesias) and post-operative pain management (opioids). Then people discovered they could medicate themselves and the rest was history...