When Thanos was first revealed in the mid-credits scene of the original Avengers, Marvel fans had a hint of what that madman Feige was setting up. But the director of the movie had no idea what to do with the Mad Titan.
Whedon explained to IGN how he wouldn’t have done Thanos as well as the Russos:
“Honestly, I kind of hung [Thanos] out to dry,” Whedon said of how he first teased Thanos. “I love Thanos. I love his apocalyptic vision, his love affair with death. I love his power. But, I don’t really understand it. He’s had a lot of power, and he was cool in the comics. And I’m like, Thanos is the ultimate Marvel villain! And then I was like, I don’t actually know what I would do with Thanos. So, I liked what [the Russo brothers] did so much, and I thought Josh Brolin killed it. And they did an amazing job of keeping that performance on-screen. But it wasn’t like I was like, here’s a set of directions. I was like, I’m gonna get through Ultron, nap for four years, and then I’ll come to the premiere. Which I did! It was like, this is so cool!”
Thankfully we have the Russo brothers who not only knew how to handle Thanos, but delivered something pretty incredible.