I don't think Bitcoin is the strongest currency in the world, because it honestly wouldn't take more than a few billion dollars USD in mining equipment to ruin it.
I think the cheapest and easiest way to ruin bitcoin is the propaganda being constantly spread about LN and Segwit. If a lot of people use that for their transactions they don't realize it can all be reversed by just one 51% attack miner. With how it is right now that can only happen for the last 2 or 3 blocks.BTC has a long way to go.