Tony -

Steve was your best friend because he understood your frustration with Tony

Steve -

Loki was surprisingly your best friend as you both loved to play tricks on Steve

Clint -

Bruce was your best friend as you loved science and creating new things to help Clint with his job

Bruce -

Tony was your best friend much to Bruce's regret as you both loved to annoy the hell out of him

Thor -

Steve was your best friend as you spent many afternoons teaching them both about technology

Loki -

Thor was your best friend because he was the only one who saw Loki the same way that you did