Asking here for help as I couldn’t find any answers online. I’ve been trying to get through easy combat achievements and “a slow death” is the only one remaining but I’m struggling to complete it.

According to the wiki you should be able to complete this using a blowpipe https://oldschool.runescape.wiki/w/A_Slow_Death

However after two attempts of this I haven’t got the achievement. I geared up with blowpipe and got the boss to low health and just waited for venom to kill it exactly as described on wiki strategy but no achievement. I tried it again with a serp help too in case blowpipe venom didn’t count but it still didn’t work.

Any ideas what I could be doing wrong or if this could be a bug?