A two-dimensional MXene 2D-Ti3C2Tx is prepared by two methods in this work: HF-etched (M-HF) and a less-toxic solvothermal-etched (M-ST) process that lasted 24 and 48 h, respectively. The grain size of MXene has been quantified and reported for the first time. Normal, lognormal, and Poisson distribution functions estimate the grain boundary size with standard deviation. Further, to check the accuracy of continuous grain size predictions, Regression-Based Models, i.e., Decision Trees, Random Forest (RF), and Support Vector Regression (SVR) are analyzed, providing novel insights into their structural characteristics and potential influence on material properties. The solvothermal-etched MXene (M-ST) has a higher porosity and a comparatively larger surface area. Additionally, compared to earlier preliminary research on MXenes (Ti3C2Tx), it appears to have more active sites (defects). Due to these factors, a 20 μM aqueous dye solution of methylene blue (MB) was degraded by 98.42% using just 15 mg of M-ST in 30 min under visible light. The process achieved a degradation rate constant of 0.097 min1, representing the highest dye degradation efficiency ever reported for pristine MXene. The focus of this study is to investigate the impact of defect-rich MXene on facilitating dye degradation, a novel approach. The outcome of this study provides a valuable understanding of the relationship between grain size, defects, and dye degradation. The study of MXene grain size opens new opportunities to optimize its electronic, thermal, and mechanical properties, significantly broadening its applicability across domains such as energy storage, catalysis, and nanoelectronics. Additionally, MXene demonstrated significant recyclability, allowing for repeated use, which is advantageous for environmental applications.