"以恩人态度自居的" can be translated into English as "assuming an air of a benefactor" or "acting as if one were a benefactor".
Here are some example sentences to illustrate the usage:
1、 He always assumes an air of a benefactor when helping others, which makes people uncomfortable.
(他总是以恩人态度自居地去帮助别人,让人很不舒服。)
2、 She shouldn't act as if she were a benefactor just because she lent me some money.
(她不应该仅仅因为借了我一些钱就以恩人态度自居。)