He was definitely a ruthless warlord. Most successful people in that world are ruthless.
He was both, in TES (as well as in our world, sort of) being a ruthless warlords doesn't mean that someone was not benevolent hero. Besides Talos =/=Tiber=/=Hjalti
We have a tendency to idolise warlords, even those who destroy more than they create like Alexander and Julius Caesar.
It doesn't have to be one or the other. The "wise and benevolent hero" never actually killing his enemies and always taking the moral high ground is a fairly modern notion, and one born more out of wishful thinking and naivete than anything else IMO. As is the idea that a ruthless general must by necessity be a stereotypical evil tyrant bent on iron fisted, North Korea style world domination.