This is a common question "Which sign do you think it is the most toxic?" There are a few issues with this question.
No one person is a perfect representation of any single sign. Our birth charts are made up of all twelve zodiacs with various planets in different signs and houses that play with and against each other. That angry side you see in your Leo Sun friend may actually be their repressed Aries Mars.
We all have free will, we all experience a lifetime of different privilege's and traumas that inform our personalities. While our charts can tell us a lot about ourselves, our priorities, our needs and goals - what's happening in our life and how we are healing and growing plays a huge part as well.
Each sign has both insecure and secure expressions. Every archetype has negative and positive displays. Scorpio can heal pain as expertly as it can dish it. Gemini is endlessly curious, but can be gossipy. Taurus can be trusted to always be there for you, but can be stubborn. How these signs show up depends entirely on the individual and their unique AstroSoup recipe. If you have a bad experience with a manipulative Cancer and swear off all Cancers for life, you may be robbing yourself of a nurturing and warm experience with a healthy Cancer.
For me, there are no absolutes in astrology and I find beauty in each of the archetypes insecure and secure expressions.
I urge you not to use astrology to identify "toxic" or "bad" traits - and not to judge all of an archetype based on one example.
Instead, simply focus on you! Build a deeper understanding of yourself, your needs and how you move in the world, so you can improve upon the insecure expressions and take pride in the healthy ones.