If we're assuming there are people or group who actively attack small/new cryptocurrency, you shouldn't use PoW and choose another consensus such as PoS/dPoS and assuming there's no way for any attacker to get majority of coin supply easily.
You could look into merged mining with another coin eg BTC.
This might be best idea, but useless if there's no "parent" cryptocurrency miners interested to mine minor cryptocurrency (which support merged mining obviously) since the set-up isn't easy and usually the extra profit is too small.