Is looking at foreign women and seeing their 'awrah (parts that should be covered) among the major sins? If so, what are the expiations for major sins, and what are the major sins?

Prohibited gazing is originally considered a minor sin, but it can escalate to a major sin if it is accompanied by fear of temptation (fitnah).

Scholars have differed in defining what constitutes a major sin. Some have held that it cannot be precisely defined, while others have stated that it has known criteria, such as: that for which there is a prescribed punishment (hadd) in this world or a threat of punishment in the Hereafter; that which incurs Allah's curse or wrath; that which negates faith; that which infringes upon the rights of human beings; that which carries a severe warning in a religious text; or that which necessitates a prescribed punishment.

Al-Alla'i mentioned some major sins explicitly stated in the Hadith, including: polytheism (shirk), unlawful killing of a soul, adultery, fleeing from battle, sorcery, consuming usury and the property of an orphan, slandering chaste women, giving false testimony, the false oath (al-yameen al-ghamūs), backbiting (namīmah), theft, drinking alcohol, and disrespecting parents.

Major sins are expiated only through repentance (tawbah), whereas minor sins may be expiated by good deeds. The assertion that good deeds expiate major sins is unequivocally false, for repentance is an obligation upon all servants, and it involves regret and a firm resolve not to return to the sin.

What is mentioned in some Hadith regarding certain deeds expiating sins refers to minor sins, not major ones, or it means that major sins may be effaced by balancing them with some good deeds on the Day of Judgment.