While any Altcoin is swayed by the overall market, finding an Altcoin with a large market cap and large trading volume should be a good estimator of stability. For the cheap mid-price Altcoins, something like Ripple is pretty stable. For the even cheaper coins, you can never go wrong with Dogecoin.
Even most of those altcoins with the high marker cap were red for some days together with bitcoin. The goal is to find an altcoin where I can hide my money from those dumps. Ripple performed greate this time but I see no guarantees that this coin will do the same at the next time.
for Altcoin which has an ever-increasing development will be great by keeping the stability of existing coins. so it is very good with the coins to be stable coins that are very capable of worth the future. such as the EOS which is a fairly stable coin today.