Wa `alaykum As-Salamu wa Rahmatullahi wa Barakatuh.
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
In this fatwa:
1- The most fundamental question when choosing a partner is that of his or her religious piety, but this does not mean that other considerations are to be neglected.
2- Marriage is a life-long partnership and hence each spouse should make the decision after proper study of the person he/she will live with.
Answering your question, Sheikh Ahmad Kutty, a senior lecturer and Islamic scholar at the Islamic Institute of Toronto, Ontario, Canada, states:
Since marriage in Islam is a partnership based on free choice, it is ultimately yours to decide whom you wish to marry, so long as you exercise your choice under the guidance of your parents or guardians.
Although it is recommended that you accept a proposal from a person with good morals and character, you are not obligated to marry him if his demeanor does not please you.
By this I do not wish to imply that you simply reject a proposal without proper study of the person. Rather you should ask people of integrity who know the person closely about his character and morals. If he is certainly of a harsh nature, you are not to be blamed for rejecting him.
The Prophet (peace and blessings be upon him) taught us that gentleness and leniency are very much essential ingredients of Islamic character. Indeed, they may be more valued in the sight of Allah than outward signs of piety.
So, your feeling about a person that he appears scary may not necessarily be un-Islamic.
Lastly, condition yourself to make such choices only after due deliberation and istikharah (prayer for guidance in decision making).
Almighty Allah knows best.
Excerpted, with slight modifications, from: www.islam.ca