the safest wallet is the offline wallet but there is still a risk that if the pc where you keep the offline wallet is destroyed then you can not do anything, print the wallet on a old printer with no internet connexion and no memory, then you can still lose the paper, so there is no safe, there is always a risk
It's pretty tough to get coins 100% secured because there is a lot of software that can break wallets. Just keep it encrypted and hope for the best.