I've upgraded some Heroes to platinum. Who should I focus on next?

Been spending the last few weeks upgrading non-meta units to platinum because I am a filthy casual. They were mostly 5-7 stars anyway. Do you guys have any suggestions?

Edit: also look at my boi operator he’s grown big and strong i love him

I would go with ANFE (Angry Nuclear Fission Enginer). The one sandwiched between Ronin and Halo. His Gold increases his damage equal to the damage he receives. His Platinum kills anyone he receives critical hit from.

Also, awesome operator.

Mandrake, nightengale, halo and ifrit would be my suggestion. Ifrit is most useful at play anyway.