Expensive ice that really needs 3 tokens to unfold its true strength.
A 6, 4 strength sentry is kinda cost ineffective, though unconditional tagging and program trashing are subs that hurt. But where Mausolus only gains nastier subs from tokens Colossus also gains strength.
With 3 advancement tokens Colossus becomes a powerhouse with strength 7 and two subs that the runner really wants to break. Getting two tags, presumably from a Weyland corp, means at least a rush to clear two tags and at worst (e.g. running last click) getting into BOOM! range. Having a program and a resource trashed, chosen by the corp, also means a big tempo hit.
Strength 7, 2 sub ice is not easy to break. Without a targetted Femme Fatale or a disposable breaker like Faerie (5 to boost, 0 to break) you're looking at 6 with MKUltra and Alias, 7 with Mongoose and Garrote, 8 with Ninja and Lustig.
Of course Colossus requires a major investment by the corp, at least 9 and 4 clicks to install, rez and boost to full potential, unless Anson Rose or the likes are used. On the other hand Weyland are known for not being penny pinchers and they have the tools to make advancable ice work.
It's an interesting card, high cost, high tax and woe to the runner that actually hits the subs.