I have a doubt with this card and Cable. His own side scheme, Technovirus Purge says that characters other than Cable cannot remove threat from it. My question is... ¿if I Attach Overwatch to another scheme, can I discard it to remove threat from Technovirus Purge when another character thwarts to the attached scheme?

I'd say yes, as I'm the owner of the overwatch card, and It's me who is using it, therefore, removing threat from Technovirus Purge. I'd just want to know if anybody can confirm that I'm doing right.

Overwatch is one of the strongest threat-removal cards in the game. In terms of threat removed per resource, it can easily hit the benchmark of 2 from a simple hero or ally THW activation. In combination with larger thwart events like For Justice! or Crisis Averted, Overwatch reaches 4-for-1 or 6-for-1 efficiency, nearly unmatched in the game under normal circumstances. On top of this, it costs 0, giving your hand maximum flexibility for efficient turns. Needing a second scheme to come into play could be awkward, but you can always just stick it on the main scheme and wait for one to come out. Nothing is better than the peace of mind knowing that when a nasty side scheme comes out, you'll be able to deal with it while still keeping pace on the main scheme. I'll especially add copies of Overwatch to my deck if I'm playing a few player side schemes, or if I have a One Way or Another strategy. If you're searching for cards to make your Justice deck better at thwarting, be sure you've considered Overwatch.