There have been been some particularly nasty investigator + basic weakness pairings in the past, and with the introduction of Charlie, a new one rises to the top of that list.
Stubborn Detective shuts down the front of your investigator card. For Charlie, this includes not just his ability ... but also his 3 additional ally slots. Drawing this weakness could lead to you losing up to 3 allies at once, along with their skill boosts, abilities, and soak. (and the resources and actions to put them into play). You can go from being completely secure, to being defenseless and 1/1/1/1 in the mythos phase.
For other investigators, the detective's effect is temporary e.g. Calvin can get his stats back by walking out. Unfortunately, as Charlie, your discarded allies don't come back. Another problem is that you don't have to be the one to draw Stubborn Detective; another player's Detective zaps you simply by being in the same location.
I think, once you see this guy show up on the table, you will need to make some adjustments to your deck to mitigate the carnage. Charisma shoots up in priority, obviously. If you have the correct classes, deck scrying (Scrying, Parallel Fates etc) can help, as can ally recursion (A Chance Encounter, Protecting the Anirniq). Maybe put in some non-Ally defense/soak, and skills as well. If another player has the Detective in their deck, you will be taking a great risk being at the same location, so you may wish to split up until the detective arrives and is dealt with.
This combination is on par with Lola Hayes' pre-Taboo weakness, in terms of how devastating it can be, and the amount of dread it makes you feel every time you draw a card. But at least it does make for great stories and memorable moments..?