By growing even bigger

Derek focused on being 40 feet tall - clothed, he saw that Jack destroyed his clothes and he wanted to avoid this. To his shock, he found himself increasing in size rapidly - he reached 40 feet in about five seconds. The sensation of his body expanding from within was insane - and kind of arousing.

He looked down. The tallest people in the crowd would only reach up to half his calf. Ash was staring up in shock, and his tiny, pathetic body stirred something in Derek. He considered for a second how cute the little femboy would look pressed to his monstrous cock...

He shook his head and focused on his body. His clothes scaled up, proving it could be done and Jack was just being a pervert. Derek took a few steps, causing powerful quakes, which cracked nearby structures and made some people fall down. He was pretty sure that according to the square-cube law, his body should collapse under its own weight, and he did feel a lot heavier, but also much, much stronger - he could move all this mass, no problem. He took a few more steps, feeling the concrete give way under his powerful body. It was amazing...

Wait, no, Jack. Focus on Jack.

He walked up to him. Jack was still beating his meat and rubbing his ass on the building. His green eyes went wide as he stared at Derek.

"Wow, you are amazing..."

Derek clenched his fists.

"Jack, this is not funny. Shrink down right now or I'll kick your ass."

Jack licked his lips and chuckled.

"Wow, I have some good perspective..."

Derek blushed. Jack was face level with crotch - and there was very visible semichub in his pants.

"Someone likes being the big guy, right?" Jack chuckled.