Shikamaru would honestly admit that Ino scarred him. Most people would that Ino was terrifying and aggressive and headstrong and plenty of other things. Shikamaru's list goes on and on…
Some of the things she did where scarier than others. For example when they where three years old she would throw random stuff at him… needless to say he ended up with many concussions.
When Shikamaru just turned nine and she was still eight, Ino would make him play " Save Princess Ino" with her and if he refused then she would become very-very scary.
When they were ten and she started to develop feelings for boys their own age he was terrified…not because of her this time but because of the threats her father promised him. In exchange for the gift of not dying an early death ,courtesy of Inoichi, Shikamaru would keep all "lying dogs" from laying a finger on Ino.
When they were twelve and they began to share a tent on missions, Shikamaru became scarred of Ino's sleep shopping. That's right sleep shopping. Ino would often bust out with crude phrases involving shopping at all hours of the night. Things like " Drop those shoes bitch and no one gets hurt.! This is my half off sale!" Choji also developed a fear of this and Asuma thought Ino needed major therapy after discovering this strange habbit.
When Ino got her period for the first time when they were thirteen , Shikamaru cowered at the thought of PMS. It soon became a bullet he had to dodge once a month. By the end he was just thankful to come out alive.
When Ino said she loved him , Shikamaru developed a fear like none before because he just realized that she was truly unpredictable. Even though he was overjoyed…he couldn't help fearing for his life.
When Ino pulled him closer to her bed late one night, Shikamaru became worried that her mother would catch them…or worse her father. But once she started undoing their clothes he decided that he didn't care.
Shikamaru decided that she truly was the scarriest thing he had ever witnessed but in the end he decided that it was all worth it. Despite her having some qualities that where less appealing to him, she wouldn't trade her for anything