While technically released for Diwali 2011, Mankatha broke the mold of the "hero" image. Ajith Kumar played a negative/grey-shaded character (Vinayak Mahadevan), which was rare for a lead star in Tamil cinema. Its heist plot and "Vilaiyaadu Mankatha" track drove massive demand.
While the nostalgia for a 2011 film like Ko or Aadukalam is understandable, attempting to download these files today is fraught with risk.
The landscape has shifted significantly since 2011. With the advent of OTT (Over-The-Top) platforms, many of the struggles to find high-quality versions of these older movies have been solved.