Regret
The sun was out, but the light felt too warm for Severus's comfort as he stared at the tombstones before him. He was preoccupied with thoughts in his head of how he could've acted differently toward them, wondering if he would have found them as insufferable if he'd been more patient. He would give himself some credit and not deny that their relationship had improved over the course of four decades, but reminiscence showed him his own shortcomings.
"... you never made anything easy, did you?" Severus asked the two stones. He scoffed at himself. "Neither did I, really." He looked down at the flowers set before them, the very ones he'd placed a few minutes ago. "We all miss you. Yes, even me... We'll see each other again on the other side."
Severus took a deep breath, turned, and walked away from the graves of Peter and Petunia Pettigrew.