I still find it EXTREMELY unlikely that Fredo had malicious intent. Just doesn’t fit his character. You can be resentful without actively trying to harm the person you have resentment for. As for the drapes as others have says we dont even know if Fredo opened them and even if he did I doubt it was because he was trying to kill his brother. Fredo is guilty of being an idiot but other than that loves his brother as we saw in the flashback scene. Look I get it Mike is the main character so the initial reaction is to root for his and justify his actions. And look when it comes to guys like Barzini, Roth, Carlo, and Tessio Mike’s actions are justified. But when it comes to Fredo it’s not