My sister can not only irritate me to a great extent, but also make some of my biggest nightmares come true.

how's this for a thesis?

Smoother phrasing -

My sister not only irritates me to a great extent, but she also makes some of my worst nightmares come true.

(Nightmares have no size!)

ok, thanks

Your proposed thesis statement suggests that your sister not only irritates you but also has the ability to make your nightmares come true. However, it lacks a clear direction and does not provide any supporting arguments or evidence.

To improve your thesis statement, you can start by focusing on a specific aspect or impact of your sister's behavior. Consider the following revised thesis statement:

"Through her persistent actions and manipulative behavior, my sister not only exasperates me but also has the power to disrupt my peace of mind and make my worst fears manifest."

This revised thesis statement sets a clear direction for your essay by highlighting the key features of your sister's behavior and potential effects on your well-being. It also suggests that you will discuss the ways in which she causes irritation and induces nightmares.

Remember to provide specific examples and evidence to support your claims throughout your essay.