英语道歉信的万能结尾需兼顾表达诚意与提供补救方案，以下为综合推荐：

1. 核心道歉表达

   • "I hope you can accept my apologies. Please allow me to say sorry again."（希望你能接受我的道歉，允许我再次致歉）

   • "Once again, I am sorry for any inconvenience caused."（对于所造成的不便，我再次道歉）

   • "I do apologize for any inconvenience this may cause you."（对于给你带来的不便，我深感抱歉）

2. 主动提供补救方案

   • "I would be very grateful if you could tell me if there is any way that I can make up for it."（若能弥补，恳请告知具体方式）

   • "I hope you can pardon me for this matter again."（希望你能再次原谅此事）

3. 强调诚意与态度

   • "To be frank, I completely forgot about it until it was too late, and I am very ashamed of myself, hoping you will forgive me."（坦白失误，表达悔意）

   • "I regret to inform you that I am unable to do..."（遗憾地说明无法履行承诺）

注意事项 ：避免使用模糊表达（如"Sorry"），建议结合具体事件说明原因，并提供实际补救措施以增强诚意。